JP2018001230A - Method and device for production of double tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for efficiently producing a high-quality double tube having sufficient fitting stress by preventing evagination breaking of an inner tube or buckling of an outer tube.SOLUTION: A production method for a double tube comprises previously heat-expanding an outer steel tube 1, relatively layering an inner steel tube 2 into an outer steel tube 1, contacting the inner tube 2 with the inner face of the outer tube by hydraulic tube expansion of the inner tube 2 to integrate, and cooling and contracting the outer tube 1 to fasten the inner tube to fit in the outer tube. In the hydraulic tube expansion of the inner tube 2, an axial tension balance is adjusted by imparting an axial tension in a direction compensating the hydraulic axial tension generating accompanying the hydraulic tube expansion of the inner tube 2 to a slide head 11 slidable in an axial direction while supporting the inner tube 2 by an axial tension compensating cylinder 12.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method and an apparatus for producing a double pipe used for a line pipe, an oil well pipe, a corrosion resistant steel pipe for a chemical plant, etc., wherein an outer steel pipe is mainly made of carbon steel and an inner steel pipe is mainly made of a corrosion resistant steel pipe.

  In the production of such a double pipe, it is difficult to apply a proper fitting stress to the tight fitting surface of the outer steel pipe and the inner steel pipe, and a uniform and predetermined fitting stress is given over the entire length of the double pipe, There is a demand for a double pipe manufacturing method and a double pipe manufacturing apparatus having excellent quality and high productivity (hereinafter, the inner steel pipe is also referred to as “inner pipe” and the outer steel pipe is also referred to as “outer pipe”).

  9 and 10 show a conventional example of a double pipe manufacturing method and a double pipe manufacturing apparatus, which are described in Japanese Patent Publication No. 56-48255 (hereinafter referred to as “Patent Document 1”) and Japanese Patent Publication No. 63-16210. (Hereinafter referred to as “Patent Document 2”).

  Of these, FIG. 9 is a copy of the illustration of the embodiment shown in FIG. However, since the reference numeral of Patent Document 1 overlaps with the reference numeral of the present invention, the reference numeral of FIG. In this patent document 1, “both ends of the inner tube 103 are formed with an inner tube 104 by a plug body 105 and a plug body 105 ′, the inner tube 202 is inserted into the outer tube 101, and the outer tube is After being heated and expanded by the coil heater 102, the liquid is supplied from the hole 106 of the perforated plug body 105 in the liquid supply direction 107, and the inner tube 103 is expanded in the pressurizing direction 108 indicated by the arrow to the inner portion 104, so Then, the pressure on the inner tube 103 is released, and a predetermined tightening margin is formed on the inner tube 103 and the outer tube 101 by thermal contraction of the outer tube 101 ”(page 2, right column, lines 3 to 38). (Summary of line) A method of manufacturing a double pipe is disclosed. However, although the concept of the above-mentioned double pipe manufacturing method is disclosed in Patent Document 1, the size of the inner pipe and the outer pipe, the various manufacturing conditions such as pipe expansion, the quality of the fastening allowance, etc. There is no disclosure of the above, and there is no disclosure of a technique for dealing with the axial contraction of the inner tube during tube expansion.

  Next, FIG. 10 is a copy of the explanatory diagram of the embodiment shown in FIG. However, since the code of Patent Document 2 overlaps with the code of the present invention, 2 or 20 is added to the code of FIG.

Patent Document 2 has the following description as a premise of the embodiment shown in FIG.
“In the meantime, in the embodiment shown in FIG. 3, since the step portion 27 is formed in the slide portion of the shield head 6 with respect to the core 17 ′, is there any reaction force against the shield head 6? Also, for this reason, the embodiment shown in FIG. 3 has an advantage that the double pipe can be easily manufactured because the contraction force of the inner pipe 2 can be easily obtained. .
In addition, in the embodiment shown in FIG. 3, the stepped portion 27 is positively made larger in diameter than the expansion tube 21 at the front thereof, thereby positively rejecting the axial contraction force on the inner tube 2. There is a merit that manufacturing is easy because it can be enlarged. (Page 4, right column, lines 27-39)

  Furthermore, the structure of FIG. 4 of patent document 2 is demonstrated using FIG. The piston rod 219 ′ integrated with the piston of the hydraulic cylinder 218 ′ is connected to the cored bar 217 via the shield jaw 208 ′, and fixed to the tip flare 203 ′ of the inner tube 202 by a nut 225 in a liquid tight manner. It is a structured. The inner tube 202 has a structure in which a base flare 203 of the inner tube is fixed and connected to the seal head 206 ″ from a base of the seal head 206 ″ via a movable seal 206 ′ fixed by a bolt 209. The cored bar 217 is integrated with the stand 216, and the hydraulic cylinder 218 'is also fixed to the stand 216 with bolts. The expanded pipe flow passage 211 includes a base flare 203 and a tip flare 203 ′ of the inner pipe 202, and is slidable at the rear end portion of the seal head 206 ″ via the seal 220 to the external cylinder 228 provided on the stand 216. And it has a liquid-tight structure.

  According to the above-mentioned structure disclosed in FIG. 4 (FIG. 10) in Patent Document 2, “As such technical means, an external cylinder 228 is formed outside the base portion of the cored bar 217 as shown in FIG. The outer cylinder 228 is slidable in the axial direction via the seal head 206 ″ and the seal 220, and the outer cylinder 228 and the expansion chamber 221 are communicated with each other via the expansion flow passage 211 inside the seal head. However, the axial reaction force on the inner tube 202 is positively eliminated by eliminating the axial reaction force by making the inner diameter of the outer cylinder 228 equal to or larger than the inner diameter of the inner tube 202. Can be given. (Page 4, right column, line 40 to page 5, left column, line 6).

  However, in FIG. 10, adjusting the diameter of the outer cylinder 228 to the inner diameter of the inner tube 202 means that the stand 216 and the core metal 217 must be replaced with each other as the inner diameter size of the inner tube 2 changes. Also, since the inner surface of the outer cylinder 228 has a structure in which the rear end of the seal head 206 ″ is liquid-tight and can slide through the seal 220, the seal head 206 ″ must also be replaced. It is difficult to prevent the inner tube 202 from bulging and breaking or the outer tube 201 from buckling by eliminating the influence of the axial contraction force.

Japanese Patent Publication No. 56-48255 Japanese Examined Patent Publication No. 63-16210

  The problem to be solved by the present invention is to investigate many specific techniques not disclosed in the above-mentioned prior art in the manufacture of double pipes, and prevent the inner pipe from bulging and breaking or the outer pipe from buckling. Thus, an object of the present invention is to provide a technique for efficiently producing a high-quality double pipe having a sufficient fitting stress.

The present invention provides the following (1) to (5) double pipe production method and (6) to (9) double pipe production method.
(1) The outer steel pipe is thermally expanded in advance, the inner steel pipe is relatively overlaid on the outer steel pipe, the inner steel pipe is hydraulically expanded and brought into contact with the inner surface of the outer steel pipe, the outer steel pipe is cooled and contracted, and both the steel pipes are tightened. In the double pipe manufacturing method to be fitted,
When the inner steel pipe is hydraulically expanded, an axial force in a direction that compensates for the hydraulic axial force generated by the hydraulic expansion of the inner steel pipe is applied to the slide head that is slidable in the axial direction while supporting the inner steel pipe. And adjusting the axial force balance.
(2) The double pipe manufacturing method according to (1), wherein the outer steel pipe is heated to 100 to 500 ° C. and thermally expanded in advance.
(3) The double pipe manufacturing method according to (1) or (2), wherein when the inner steel pipe is relatively layered on the outer steel pipe, the inner steel pipe is cooled with cooling water of 30 ° C. or lower.
(4) The supply stage of the high-pressure water when the inner steel pipe is expanded with water is set to two or more stages, and the time until the high-pressure water reaches a predetermined maximum pressure in the final stage is 0.5 to 5 seconds, (1) The method for producing a double pipe according to any one of to (3).
(5) After the inner steel pipe and the outer steel pipe are tightly fitted into a double pipe, high pressure water is supplied to the water passage when the inner steel pipe is hydraulically expanded, and the double pipe water pressure test is performed. (1) The method for producing a double tube according to any one of to (4).
(6) The outer steel pipe is thermally expanded in advance, the inner steel pipe is relatively overlaid on the outer steel pipe, the inner steel pipe is hydraulically expanded and integrated with the inner surface of the outer steel pipe, the outer steel pipe is cooled and contracted, and both the steel pipes are tightened. In the double pipe manufacturing equipment to be fitted,
An axial force compensation cylinder that adjusts the axial force balance by adding an axial force in a direction that compensates for the hydraulic axial force generated by the hydraulic expansion of the inner steel pipe to a slide head that supports the inner steel pipe and is slidable in the axial direction. A double pipe manufacturing apparatus characterized by being provided.
(7) The double pipe manufacturing apparatus according to claim 6, further comprising a water supply / drainage mechanism for supplying or draining cooling water or high pressure water to the slide head and the axial force compensation cylinder.
(8) The double-pipe manufacturing apparatus according to (7), wherein the water supply / drainage mechanism includes a booster that receives water from a water supply tank and receives high-pressure oil from an oil circulation system to supply high-pressure water.
(9) The double pipe manufacturing apparatus according to (8), wherein the booster includes a plurality of stages.

  According to the double pipe manufacturing method and the double pipe manufacturing apparatus of the present invention, the axial force balance is adjusted by applying the axial force in the direction to compensate for the hydraulic axial force generated with the hydraulic expansion of the inner steel pipe. Therefore, it is possible to efficiently manufacture a high quality double pipe having a sufficient fitting stress by preventing the inner pipe from bulging and breaking or the outer pipe from buckling due to the influence of the axial contraction force of the inner pipe. it can.

It is a flowchart which shows each process of the double pipe manufacturing method of this invention, and shows the structure of one Embodiment of this invention. It is a schematic diagram of the double pipe manufacturing apparatus which shows each process (basic process AD) which implements the double pipe manufacturing method of this invention, and shows the structure of one Embodiment of this invention. FIG. 3 is a detailed view of basic steps A, B, and C shown in FIG. 2, and is a view in which an outer tube is relatively layered on a mandrel. FIG. 3 is an enlarged schematic view of the axial force compensation cylinder, slide head, ram, and mandrel shown in FIG. 2. FIG. 4 is a schematic diagram showing a process of converting the inner steel pipe and the outer steel pipe into a double pipe in the double pipe manufacturing process of the present invention shown in FIG. It is a graph which shows the relationship between the pipe diameter in the double pipe manufacturing process shown in FIG. 5, and the fitting stress of an inner steel pipe and an outer steel pipe. It is the schematic diagram which shows the heating process and heating furnace of an outer steel pipe among the double pipe manufacturing processes of this invention shown in FIG. 2 by the BB cross section of the same figure. It is a schematic diagram of the double pipe manufacturing apparatus which installed 1 system which supplies / discharges 3 lines, cooling water, etc. with the double pipe manufacturing apparatus shown in FIG. It is a schematic diagram of the example which shows the conventional double tube manufacturing method described in patent documents 1. It is a schematic diagram of the example which shows the conventional double pipe manufacturing apparatus described in patent document 2.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 1 is a flowchart of an embodiment showing each step of the double pipe manufacturing method of the present invention. A1 to A4 shown in the figure are steps for producing an inner pipe to be internally attached to a double pipe (generally also referred to as a liner) using a corrosion-resistant steel pipe produced by a general production method. A2 is a process in which a part of both ends of the inner pipe is thinly extended and processed into a flare outward or inward, and A3 is so as to cover the mandrel of the double pipe manufacturing apparatus described later on the flare-processed inner pipe. Step A4 is a step of cooling the inner pipe attached to the mandrel by receiving cooling water from a cooling water supply mechanism (water supply / drainage mechanism) described later.

  B1 to B4 shown in the figure are steps for manufacturing an outer pipe which is a steel pipe outside the double pipe using mainly a carbon steel pipe manufactured by a general method. B2 is a cleaning process for removing rust and dirt in the outer pipe, B3 is a process for loading the outer pipe into a heating furnace, and B4 is a process for heating the outer pipe and moving while maintaining the heating temperature.

  Next, C1 to C4 shown in FIG. 1 are processes for manufacturing a double pipe by relatively layering an inner pipe and an outer pipe. C1 is a process of moving the outer tube heated in the B process so as to cover the cooled inner tube loaded in the mandrel in the above A process, and C2 is supplying a high pressure water to the gap between the mandrel and the inner pipe. The expanded inner pipe is expanded and the inner pipe comes into contact with the inner surface of the outer pipe by the expansion. After continuing the expansion, the supply of high-pressure water is stopped, the cooling water is passed, and the outer pipe is thermally contracted. The inner tube and the outer tube are tightly fitted to form a double tube, C3 is a step of pulling out the double tube from the mandrel, and C4 is a step of processing the end of the double tube. C5 shown in the figure is a step in which a double-pipe water pressure test is optionally carried out after maintaining the gap between the double-pipe and the mandrel and the water tightness of the high-pressure water chamber after forming a double-pipe.

Hereafter, each manufacturing process shown in FIG. 1 and another process are demonstrated in detail.
FIG. 2 shows a basic line for carrying out the present invention, and the lines are referred to as a basic process A, a basic process B, a basic process C, and a basic process D for each process. In FIG. 2, the basic process B to the basic process D are linear devices aligned with the central axis of the mandrel 4, but for convenience of illustration, they are shown in a two-stage display cut by the symbols ho and ho ′.

<Basic process A: Cooling water storage and supply, high pressure oil generation system and high pressure water supply>
Referring to FIG. 3 together with FIG. 2, in the basic process A, the high-pressure water supply path is such that the pump 24 connected from the water storage tank 22 through the water supply pipe to the supply port 15 of the ram 3 through the water distribution pipe 42. ′ Is connected to the booster 30. The booster 30 receives the high-pressure oil supplied from the accumulator 36 through the high-pressure oil pipe 37 and supplies high-pressure water to the ram 3 and the axial force compensation cylinder 12 through the high-pressure water pipes 41, 41 ′ and 41 ″. The oil discharged from the cylinder chamber is sent to the hydraulic unit 35 through the oil pipe 37 ′, and the oil is stored in the accumulator 36 in a high pressure state.

<Basic process B: Axial force adjustment by ram 3, slide head 11 and axial force compensation cylinder 12>
Referring to FIG. 2, in the basic process B, the axial force adjusting mechanism is a slide head provided so as to grasp (enclose) the rear end portion of the ram 3 and the mandrel 4 fixed to the fixed frame 8 provided on the mount 54. 11. A connecting rod 10 and a moving beam 9 provided on the slide head 11 are provided, and the moving beam 9 is connected to a piston rod of an axial force compensating cylinder 12 fixed to a fixed frame 8 ′.

<Basic Step C: Mounting the Inner Tube 2 to the Tip of the Slide Head 11 and the Mandrel 4>
Referring to FIG. 2, in the basic process C, the mandrel 4 that is integrated with the ram 3 is supported by a mandrel support device 50 that is tilted by an elevating air cylinder 51 in the direction of an arrow 53 installed on a pedestal 54.

<Basic Step D: Heating, Rotating, and Moving of Outer Tube 1 Consisting of Heating Furnace 60, Outer Tube Rotating Device 79, Moving Car 64, and Drive Device>
Referring to FIG. 7 together with FIG. 2, the heating furnace moving carriage 64 on which the heating furnace 60 that runs on the rail 52 installed on the gantry 65 in the basic process D is reciprocated in the direction of the arrow 71 by the heating furnace moving motor 69. To do. The outer tube 1 is mounted on an outer tube rotating roll 79 and is connected to a rotary chuck 66 that rotates the outer tube 1. The rotary chuck 66 is connected to a rotary chuck moving motor 67 and reciprocates in the direction of arrow 70.

  FIG. 3 is a detailed view of the basic steps A, B, and C, and is a view in which the outer tube 1 is relatively layered on the mandrel 4. Based on FIG. 3, the structure and partial operation of the apparatus of the present invention will be described in the order of manufacturing steps.

  The booster 30 includes a primary cylinder chamber 43, three-stage secondary cylinder chambers 31, 32, 33, and pistons 39, 39 ′, 39 ″, and a cross-sectional area of the primary cylinder chamber 43 and a secondary cylinder. The pressure of the high-pressure water discharged from each secondary-side cylinder chamber varies depending on the ratio of the cross-sectional area of the chamber, and the pressure of the high-pressure water supplied by arbitrarily combining the discharge ports of the secondary-side cylinder chamber Can be set.

  In the basic process A, the cooling water storage tank 22 supplies the cooling water to the ram 3 via the cooling water supply valve 23, the cooling water supply pump 24, and the check valve 25, and the booster water supply electromagnetic valve 26 and the reverse. Cooling water is supplied to the three-stage secondary cylinder chambers 31, 32 and 33 of the booster 30 via the stop valve 27. Each cylinder chamber on the secondary side of the booster 30 is provided with a high-pressure water discharge port, and the high-pressure water supply pipes 41, 41 ′ and 41 ″ provided at the discharge port have high-pressure water supply electromagnetic valves 40, 40 ′ and 40 ″. Is installed. The high-pressure water supplied by the booster 30 is controlled by the high-pressure water supply electromagnetic valves 40, 40 ′ and 40 ″ according to the set pressure necessary for the pipe expansion, and selected alone or in combination, and is mainly pressurized by the supply pipe 41. It is supplied to the ram 3 and the axial force compensating cylinder 12 through the electromagnetic valve 46.

  The cooling water in the water storage tank 22 is cooled by a cooler, a cooler or the like (not shown), and is preferably maintained at 30 ° C. or lower, and 5 ° C. or lower as required.

  The hydraulic unit 35 receives supply of waste oil from the primary side cylinder chamber 43 of the booster 30, compresses the waste oil, supplies it to the accumulator 36 as high pressure oil, stores the oil, and stores the high pressure oil in the primary side cylinder chamber when the pipe is expanded. 43. The hydraulic unit 35, the accumulator 36, and the primary cylinder chamber 43 are an oil circulation system that supplies and discharges in the directions of arrows C, C ', and C "having a closed structure.

  Next, in the basic processes B and C, the ram 3 and the mandrel 4 have an integral structure, the base of the ram 3 is fixed to the fixed frame 8, and a hollow having a passage 16 for cooling water or high-pressure water provided in the center. This is a cylindrical structure. Referring to FIG. 4 together with FIG. 3, the distal end portion 6 of the mandrel 4 includes a seal disk 5 and a fastening nut 7 that fix the water passage 16 (a) and the distal end flare 73 of the inner tube 2. The slide head 11 has a drain port 19 at the center and a seal jaw 18 for fixing the end flare 74 of the inner pipe 2. The slide head 11 is installed so as to grasp (enclose) the base portions of the ram 3 and the mandrel 4, the water passage 16 (b) is provided at the front end portion of the slide head 11, and the watertight seal 72 is provided at the rear end portion. Yes. Accordingly, the slide head 11 has a structure capable of sliding (sliding) the contact surface with the mandrel 4 in the axial direction in a watertight manner through the watertight seal 72 while supporting the inner tube 2.

  The axial force compensation cylinder 12 fixed to the fixed frame 8 ′ is installed on the same axis as the ram 3. The high pressure water receiving port 14 is provided in the right chamber, and the moving beam connected to the piston 13 and the piston rod of the cylinder 12. 9 and the connecting rod 10 are connected to the slide head 11.

  The mandrel 4 is inserted so as to cover the mandrel 4 with a predetermined length of the inner tube 2 having inward flares 73 and outward flares 74 at both ends. An outward flare 74 of the inner tube 2 is fixed by a seal jaw 18 provided on a slide head 11 slidably mounted on the ram 3 and the mandrel 4, and an inward flare 73 at the tip of the inner tube 2 is fixed to the mandrel 4. The front end 6 is fixed with a tightening nut 7 via a seal disc 5. When the inner pipe 2 is fixed by the seal jaw 18 and the seal disk 5, the gap between the mandrel 4 and the inner pipe 2 forms a watertight water passage or a high-pressure water chamber 17.

  FIG. 4 is an enlarged view of the basic steps B and C shown in FIG. 3. In the pipe expanding mechanism including the axial force compensating cylinder 12, the slide head 11, the ram 3 and the mandrel 4, the inner pipe 2 or the outer pipe 1 made of high-pressure water is shown. Axial force Fr and Fl acting to the left or right of the inner tube 2 generated when the tube is expanded, and the diameter d of each part (the outer diameter dr of the ram, the inner diameter dc of the slide head 11, the inner diameter dt of the tip of the slide head 11, the inner It is explanatory drawing regarding the axial force balance by the internal diameter dp of the pipe | tube 2, and the outer diameter dm of the mandrel 4. FIG.

  FIG. 5 shows a cross-section of the process of converting the outer tube 1 and the inner tube 2 from the single tube to the relative multi-layer, the expanded tube, and the double tube in the double tube manufacturing process of the present invention shown in FIG. The cross-sectional view shows the AA cross section of FIG. From the left, these cross-sectional views are the first stage (the inner tube 2 is fitted on the mandrel 4 and the outer tube 1 is heated), the second stage (the outer tube 1 is relatively layered on the inner tube 2), and the third stage (high pressure water The inner tube 2 is expanded to the inner surface of the outer tube 1 by the water pressure P, the fourth stage (the inner tube 2 and the outer tube 1 are integrally expanded and fitted), the fifth stage (the water pressure P is released, the double tube is Cooling).

  FIG. 6 is a graph showing changes in the tube diameter D of the inner tube 2 and the outer tube 1 and changes in the tube expansion stresses σ1 and σ2 in the double tube manufacturing process shown in FIG.

In FIG. 6, the horizontal axis represents changes in the diameter D of the outer tube 1 and the inner tube 2, and the vertical axis represents changes in the stresses σ1 and σ2 in the diameter direction of the outer tube 1 and the inner tube 2. Expansion and contraction of the outer tube 1 is indicated by a bold line, and expansion and contraction of the inner tube 2 is indicated by a dotted line. The outer tube 1 is the tube expansion within the elastic limits of the steel pipe material, the outer diameter D _LO inner diameter D _PO and the inner pipe 2 of the outer tube 1 is the same size, further continued expanded pipe in continuous high-pressure water supply However, the water pressure P is released within the elastic limit of the outer tube 1 and under the condition of σ2> σ1. Next, the outer tube 1 and the inner tube 2 that have become double tubes are thermally contracted by the cooling water flowing in the inner tube, that is, the diameter is reduced, and stress is generated on the fitting surfaces of both the tubes.

  FIG. 7 is a schematic cross-sectional view of the heating furnace 60 mounted on the movable carriage 64, showing the BB cross section of FIG. A two-layer refractory brick 75 mounted on a movable carriage 64, and a furnace side wall 80 are erected so as to sandwich the refractory brick 75, and a side wall refractory material 76-1 and a ceiling refractory material 76- are provided inside the furnace body side wall 80. 2 forms a tunnel-shaped furnace. In the furnace, a roll support shaft 77 is passed between the furnace body side walls 80 on both sides, and the rotary roll 79 of the outer tube 1 is installed on the roll support shaft 77. The rotary roll 79 is removed by a roll center adjusting jig 78. The center of rotation of the tube 1 is aligned with the center of the mandrel 4. The heating of the outer tube 1 uses the combustion flame (fuel: eg, LPG) of the gas burner 63 provided on the side wall 80 of the furnace as a heating source, and the combustion gas is released by adjusting the exhaust damper 61 to adjust the temperature inside the furnace. The heating temperature of the outer tube 1 is measured by, for example, the radiation thermometer 62 to control the temperature of the outer tube 1.

  The outer tube 1 drives the furnace lid opening / closing rod 83 by the hydraulic cylinder 82 through the side wall opening / closing frame 81 and pivots in the direction of arrow 85 together with the ceiling refractory material 76-2 about the outer lid rotation shaft 84 as a fulcrum. Is opened and loaded into the heating furnace. The left outer end of the loaded outer tube 1 is gripped by a rotary chuck 66 (see FIG. 2) and arbitrarily rotated. When the outer tube 1 is heated to a predetermined temperature, the outer tube 1 moves forward (to the left in FIG. 2) by the moving carriage 64 and forms a relative multi-layer so as to cover the inner tube 4 fitted to the mandrel 4. .

  FIG. 8 is a schematic diagram of a double pipe manufacturing apparatus in which three lines of the double pipe manufacturing apparatus shown in FIG. 2 and a set of cooling and high pressure water supply / discharge systems (supply / drainage mechanisms) are installed.

  In FIG. 8, the double pipe manufacturing apparatus includes a “manufacturing apparatus line 1”, a “manufacturing apparatus line 2”, and a heating furnace 60 mounted on the axial force compensation cylinder 12, the slide head 11, the mandrel 4, and the movable carriage 64. “Manufacturing equipment line 3” is installed in parallel, and only one hydraulic system including a hydraulic unit 35 and an accumulator 36 for supplying and discharging high pressure oil to and from the booster 30 is installed. The high-pressure water supply pipe 41 supplied from the booster 30 and the cooling water supply pipe 42 supplied from the cooling water supply pump 24 are branched from the supply water to the production apparatus lines 1 to 3. This is equipment with 87, 88 and 89 installed.

  That is, the double pipe manufacturing facility shown in FIG. 8 uses a system that supplies and discharges one cooling water or the like with a control device (not shown) to match the progress of the manufacturing process of each manufacturing line with respect to three manufacturing equipment lines. Supply and drain the necessary cooling water or high-pressure water in a timely manner.

  In addition, the above embodiment is an example of an apparatus for performing the manufacturing method of the present invention, and is an example of the double pipe manufacturing apparatus of the present invention, and the present invention is limited to the above-described structural apparatus and example of equipment. Instead, it can be changed within the scope of the technical idea of the present invention.

  Next, the means and phenomenon of the double pipe manufacturing method of the present invention and the structure and operation of the double pipe manufacturing apparatus will be described with reference to FIGS.

(1) Set of inner pipe, formation of water passage and high-pressure water chamber The inner pipe 2 of the row A process shown in FIG. 1 has an inward flare 73 and an outward flare 74 processed at the end, and the mandrel shown in FIG. 4 is inserted so as to cover the mandrel 4 with the outward flare 74 first from the free end side. As shown in FIG. 3, the inner tube 2 inserted so as to cover the mandrel 4 has an outward flare 74 in a watertight manner by the shield jaw 18 at the tip of the slide head 11 and an inward flare 73 at the tip of the mandrel. It abuts on the portion 6 and is clamped in a watertight manner by a clamping nut 7 with the seal disk 5 interposed therebetween. Further, the slide head 11 has a structure that is watertight and can slide in the axial direction by a watertight seal 72 provided between the slide head 11 and the high pressure water by closing the drainage electromagnetic valve 20 of the drainage port 19 of the slidehead 11. A chamber 17 is formed.

(2) Deaeration of water passage, cooling of inner steel pipe Water flow to the inner pipe 2 set in the mandrel 4 is reversed from the cooling water pump 24 by opening the cooling water supply valve 23 from the water storage tank 22. The cooling water supplied to the cooling water supply port 15 of the ram 3 through the water pipe 42 by opening the valve 25 is passed through the cooling water passage 16 and the water passage 16 (a) in the mandrel 3. The cooling water fills an annular water passage formed in the gap between the mandrel 4 and the inner pipe 2, or the high-pressure water chamber 17, is drained from a drain port 19 provided in the slide head 11, and is stored in the distribution pipes 21 and 21 ′. Return to tank 22 and circulate.

  By this water flow, air in a series of water passages and the like is discharged, and various problems such as explosion due to water evaporation due to residual air when the heated outer tube 1 is inserted are avoided and the inner tube 1 is cooled. The cooling water prevents the inner tube 2 from being heated when the heated outer tube 1 is inserted. The water returned to the water storage tank 22 is cooled to preferably 30 ° C. or less, more preferably 10 ° C. or less, by a cooler, a cooler or the like (not shown).

(3) Heating of outer steel pipe The outer pipe 1 of the row B process shown in FIG. 1 is cleaned by polishing with a rotating brush and the like, and loaded into the heating furnace 60 shown in FIG. 2 and the basic process D shown in FIG. And heating to a temperature of 100 ° C to 500 ° C.

  As shown in FIG. 7, the outer tube 1 includes a furnace lid opening / closing frame 81 that is integral with a ceiling refractory material (for example, mineral wool) 76-2 of the heating furnace 60, and a hydraulic cylinder with a furnace lid rotating shaft 84 as a fulcrum. 82 and the furnace lid opening / closing rod 83 are opened in the furnace lid opening / closing direction 85 and placed on a steel tube rotating roll 79 provided at the center of the heating furnace 60. The placed outer pipe 1 is made to coincide with the axis of the mandrel 4 described above by the steel pipe axis adjusting jig 78, that is, the axis of the inner pipe 2 set in advance in the above (1) inner pipe setting step.

  After setting the outer tube 1 in the heating furnace 60, the furnace cover is rotated and closed by a furnace cover opening / closing device, and heated by the flame of the gas burner 63. Meanwhile, the outer tube 1 is rotated by a steel tube rotating roll 79, the heating temperature of the outer tube 1 is measured by a radiation thermometer 62 as needed, and the total length of the outer tube 1 is adjusted by adjusting the heating power of the gas burner 63 or the exhaust amount of the exhaust damper 61. Over a uniform and predetermined temperature.

(4) Cooling procedures after preparation for expansion such as setting of inner and outer pipes, pipe expansion with high-pressure water supply, and double pipe formation

a) Injection of water into the booster, injection of cooling water into the inner pipe, and completion of preparation for expansion and pressurization The basic process A shown in FIG. 3 is performed from the booster 30 by the cooling water supply mechanism to the booster 30 and the oil circulation system that sends high-pressure oil. This is a step of supplying high-pressure water to the ram 3 and the axial force compensation cylinder 12.

  When the booster water injection push button is first pressed as an operation for returning the booster 30 to the origin on the control panel (not shown), the booster water supply electromagnetic valve 26 is opened, and after a predetermined time, the motor valve 45 and the main pressurization valve 46 are opened. Is closed, the high pressure water supply electromagnetic valves 40, 40 ′ and 40 ″ are opened, the cooling water pump 24 is activated, and the pistons 39, 39 ′ and 39 ″ of the booster 30 return to the origin. When the booster 30 returns to the origin, the booster water injection operation stops after a predetermined time.

  Next, the water injection to the water passage 17 formed by the inner pipe 1 and the mandrel 4 is performed with the booster 30 at the origin and water-tight formation with the mandrel 4 and the inner pipe 2 in the pipe expanding mechanism as described in the above section (1). Completion is a condition of water injection. When these conditions are met and the water injection ON push button to the water passage 17 is pushed, the motor valve 45 is opened, the cooling water pump 24 is activated, and the water storage tank 22 is passed from the drain port 19 of the ram 3 through the drain pipe 21. The flow of water is confirmed, and the process is terminated with a push button for turning off water to the water passage 17. When the water injection to the inner pipe 1 is finished, the display of “Ready for pipe expansion” on the control panel flashes.

b) Tube insertion / relative layering with inner tube The outer tube 1 heated in advance to 100 ° C. to 500 ° C., for example, 350 ° C. by the heating furnace 60 in the basic process D shown in FIG. It moves by the drive of the heating furnace moving motor 69 in the direction 71, and is relatively layered so as to cover the already installed and cooled inner tube 2. In order to prevent the temperature of the inner tube 2 from rising during the relative multi-layering, the inner tube 2 is cooled by continuously passing cooling water through the water passage 17 of the inner tube 2 once completed in the step a).

  As a result, the pressurization mechanism side is ready for pressurization, the outer tube 1 on the tube expansion mechanism side is heated, and the “outer tube insertion complete” indicator light is turned on in response to the insertion completion signal, and pressurization with high-pressure water becomes possible. .

c) Pressurization start of high-pressure water, pressurization rise, maximum pressurization, and maximum pressure pressurization holding The oil pressure of the accumulator 36 reaches a set value, and the relative expansion of the outer tube 1 with the inner tube 2 on the tube expansion mechanism side When is completed, the pressurizing condition is set. Note that the hydraulic system having the accumulator 36 opens the hydraulic electromagnetic valve 34 when the piston 39 of the booster 30 is retracted, and the oil in the primary side cylinder chamber 43 flows in the direction indicated by the arrow c and is supplied to the hydraulic unit 35. The hydraulic unit 35 closes the hydraulic electromagnetic valve 38, compresses the oil, adds pressure, supplies the accumulator 36 to high pressure oil of a predetermined pressure, and stores the oil.

  In the control device, when the “pressurization start” push button is pressed, the drain electromagnetic valve 20 is closed, and after a predetermined time, the hydraulic electromagnetic valve 38 of the hydraulic system is opened, and the piston 39 of the booster 30 is activated to start the high pressure water supply electromagnetic valve. 40, 40 'and 40 "open only the valve corresponding to the target cylinder of the pressurization setting. The booster 30 is a three-stage device, but the pressure increase at the time of pipe expansion is substantially one stage by setting the pressure in each cylinder chamber. Alternatively, a pressure expansion tube composed of two stages is also possible.

  For example, the pipe expansion in three stages is performed when the pipe expansion is started by supplying high-pressure water to the high-pressure water chamber 17 and the pressure of the high-pressure water reaches the value of the first stage set in advance by “setting the pipe expansion pressure”. The process proceeds to the stage, and further proceeds to the third stage with the value of the second stage. When the value of the maximum pressure set in the third stage is reached, the high-pressure water supply electromagnetic valves 40, 40 'and 40 "and the hydraulic electromagnetic valve 38 are closed, and the pressurization is completed. The time is 0.5 seconds to 5 seconds.

  After reaching the maximum pressure and completing the pipe expansion, the drainage electromagnetic valve 20 and the main pressurization valve 46 are closed for the time set by the “pressurization stop timer” to maintain the pressurization state. The pressure holding time is preferably 0.5 seconds to 5 seconds. By holding the maximum applied pressure for a predetermined time, the inner tube 2 is uniformly adhered to the outer tube 1 and the fitting stress becomes uniform.

d) Cooling shrinkage by supplying a large amount of cooling water, cooling by a small amount After completion of pressurization and holding by high-pressure water, the drainage electromagnetic valve 20 opens at the time of "pressurization stop timer", and at this time, in preparation for the next large amount of cooling, The motor valve 45 is opened. The cooling water pump 24 is started, the double pipe is cooled, and the cooling water pump 24 stops when the time of the “cooling water injection timer” expires. Even after the mass cooling is completed, each valve continues to be in that state, and a small amount of cooling is continued by weak driving of the cooling water supply pump 24, and the “small amount cooling OFF” push button is pressed to complete one step.

(5) Tube Expansion Operation and Operation of Axial Force Compensation Cylinder and Slide Head Next, the tube expansion operation of the inner tube 2 and the operation of the axial force compensation cylinder 12 and the slide head 11 will be described with reference to FIGS.

  The high-pressure water supplied to the high-pressure water receiving port 14 of the axial force compensation cylinder 12 gives a force for the compensation cylinder piston 13 to advance in the left direction. The force of the forward movement is interlocked with the slide head 11 via the piston rod, the moving beam 9 and the connecting rod 10. The expansion action of the inner tube 2 in the expansion of the inner tube 2 by the high pressure water of the above item (4) c) is basically that the inner tube 2 expands to increase its inner diameter and contracts in the axial direction to increase the tube length. Shorten. Corresponding to the change in the length of the inner pipe 2, the flares 73 and 74 of the inner pipe 2 are fixed, and the water tightness of the high pressure water chamber 17 provided by the water tight seal 72 provided at the rear end of the slide head 11 is maintained. Is required. Further, it is desirable that the outer diameter dm of the mandrel 4 is smaller than the outer diameter dr of the ram 3 to secure a gap between the high-pressure water chambers 17 and to improve the cooling capacity and the expanding power of the inner pipe 2.

  The hydraulic axial force of the slide head 11 may adversely affect the following tube expansion work. The tensile axial force is (a) tensile stress is generated when the inner pipe 2 is expanded, (b) the inner pipe 2 (especially the neck of the seal jaw) is bulged and broken, and (c) the inner pipe 2 This causes relaxation of the watertight seal. On the other hand, the compression axial force (a) acts on the outer tube 1 to cause buckling deformation, and (b) loosens the inner tube watertight seal portion. These phenomena are major factors that adversely affect the productivity and quality of the double pipe, and in order to avoid these, the slide head 11 smoothly follows the change in the length of the inner pipe 2 in the pipe expansion process, It is necessary not to restrain the expansion and contraction of 2.

Here, the hydraulic axial forces Fl, Fr, and Fa acting on the slide head 11 in the high-pressure water chamber 17 can be obtained by the following equations 1-3.
(A) The hydraulic axial force Fl acting leftward (←) on the slide head is Fl = π / 4 · (dc ² −dr ² ) · P + π / 4 · (dp ² −dt ² ) · P Equation 1
(B) The hydraulic axial force Fr acting on the slide head in the right direction (→) is (as negative)
Fr = −π / 4 · (dc ² −dt ² ) · P Equation 2
(C) The combined hydraulic axial force Fa of Fl and Fr is Fa = Fl + Fr = π / 4 · (dp ² −dr ² ) · P Equation 3

Therefore,
dp = dr and Fa = 0: The axial force is balanced and no axial force is generated.
dp> dr and Fa> 0: In this case, the inner pipe 2 is pulled with a leftward axial force.
dp <dr and Fa <0: In this case, the inner pipe 2 is compressed with a rightward axial force.
However, the code | symbol used for the said type | formula shows the code | symbol of the diameter shown in FIG. 4, and is defined below.
dp = inner diameter when the inner tube comes in contact with the outer tube by expanding the tube dr = ram diameter of the slide head sliding portion dc = cylinder diameter of the slide head dt = cone throat (narrowest portion) inner diameter dm at the tip of the slide head = Mandrel body diameter P = tube expansion pressure.

  Therefore, the hydraulic axial force compensation method does not generate a hydraulic axial force if dp = dr, but it is uneconomical to change the ram diameter dr every time the thickness of the inner pipe 2 changes in production management. . Therefore, an axial force compensation cylinder 12 shown in FIG. 4 is provided, and high pressure water for pipe expansion is supplied to the cylinder to compensate the axial force. In addition, when dp <dr (Fl <Fr) and Fa <0 (inner tube compression pressure), the inner tube is fixed at the mandrel tip 6 (inner flare portion), and the slide head 11 moves and moves inside. This causes the tube to buckle, and the axial force compensation cylinder 12 prevents the slide head 11 from moving the inner tube 2 in the compression direction. Therefore, the operation of the axial force compensation cylinder 12 prevents the inner tube 2 from buckling. However, even with this axial force compensation cylinder 12, a great number of types must be prepared in order to completely eliminate the axial force. On the other hand, according to the calculation result, there is a considerable allowable range for the hydraulic axial force, so the number of axial force compensating cylinders 12 is not so large, and it is sufficient to prepare in stages within the range in which the axial force is calculated. . However, as a general rule, it is difficult to design a single slide head 11, ram 3 and mandrel 4 by combining a large number of axial force compensation cylinders 12 to accommodate a wide range of inner tube sizes. It is sufficient to prepare one type of mandrel 3 (including the slide head 11 and the ram 3) for each general steel pipe nominal diameter (nominal).

  Most standardly, the ram diameter dr with which the slide head 11 slides is made as large as possible, that is, the axial force compensation cylinder 12 having a capacity capable of balancing the axial force when the inner tube 2 is relatively thin is installed. The increase in the thickness of the inner tube 2 is accommodated within the capacity of the axial force compensation cylinder 12. As a result, the action on the outer tube 1 and the inner tube 2 due to the contraction of the inner tube 2 that occurs when the inner tube 2 is expanded is minimized, the occurrence of buckling deformation of the outer tube 1, and the watertight seal of the inner tube 2. The relaxation of the part can be prevented.

(6) Tube expansion pressure and control of the time The tube expansion time will be described with reference to FIGS. 5 and 6. In FIG. 5, they are divided into “first stage” to “fifth stage” in the order of the manufacturing process. However, this division is not linked to the first to third stages of the booster 30.

  In the first stage, an outer tube 1 that is an elementary tube and an inner tube 2 that is fitted to the mandrel 4 are prepared, and the outer tube 1 is heated. In the second stage, the outer tube 1 heated on the inner tube 2 is relatively overlaid, and the AA cross section of FIG. 3 is shown. In the third stage, high-pressure water is supplied to the high-pressure water chamber 17 in order to expand the inner pipe 2, and radial pressure P is activated on the inner surface of the inner pipe 1, and only the inner pipe 2 first expands in the circumferential direction. The pipe is expanded under plastic deformation beyond the yield point, and is inscribed in the inner surface of the outer pipe 1 at a point P1. In the fourth stage, the pressure P continues to rise and the outer pipe 1 is loaded through the inner pipe 2 and is expanded together with the inner pipe 2 to reach the maximum pressure in the third stage of the booster 30. To complete a double pipe. Next, in the fifth stage, the double pipe stops supplying high-pressure water and maintains the maximum water pressure P for a predetermined time, then opens the drain electromagnetic valve 20 and continuously supplies a large amount of cooling water. Then it cools and shrinks. The maximum pressure of the high-pressure water at the time of integral pipe expansion is the tip point P2 indicated by the thick solid line shown in FIG. 6, but this pressure P2 is limited to the elastic range of the steel pipe material of the outer pipe 1 and the pipe expansion pressure and the pipe expansion time. Set.

  The fitting stress between the inner tube 2 and the outer tube 1 is governed by the expansion stresses σ1 and σ2 at the end of the fourth stage of the inner tube and the outer tube, and the contraction amount due to cooling in the fifth stage. Therefore, it is desirable to suppress the temperature rise of the inner tube 2 that occurs during the expansion of the high-pressure water as low as possible. For this purpose, the expansion time of the high-pressure water is preferably as short as possible, preferably 0.5 to 5 seconds. Control of high-pressure water for performing such pipe expansion in a short time is performed by the basic process A shown in FIG. That is, to secure the amount of water supplied to the booster 30 in order to obtain the pressure and the amount of water previously calculated or tested in the water storage tank 22 illustrated in the basic process A, while to supply predetermined high-pressure water from the booster 30, The high pressure oil for driving the booster 30 is compressed by the hydraulic unit 35 and the predetermined pressure oil is stored in the accumulator 36.

(7) Fitting of inner tube and outer tube and control of stress The adjustment of fitting stress will be described with reference to FIGS. 5 and 6.

  As described in the previous section, for tight fitting of the inner tube 2 and the outer tube 1, external force and water pressure are applied to the inner tube 2 or the outer tube 1, and both tubes are radially or axially moved by cooling or heating. Take advantage of the phenomenon of stretching. By generating the stresses generated by this expansion and contraction, for example, pipe expansion stresses σ1 and σ2 shown in FIG. 6, and then adjusting the cooling shrinkage amount, it is possible to obtain a fitting stress necessary as a double pipe when tightly fitting. it can.

In FIG. 6, the expansion and contraction of the outer tube 1 is indicated by a thick solid line, and the expansion and contraction of the inner tube 2 is indicated by a dotted line. Each change expands due to an external force, and the expansion of the outer tube 1 is particularly within the elastic limit range. First, in the third stage, the expansion of the pipe starts only from the point D _LO indicating the outer diameter of the inner pipe 2 by the supply of high-pressure water, proceeds as indicated by the dotted line, and the stress increases with the expansion. Next, in the fourth stage, the outer surface of the inner tube 2 comes into contact with the inner surface of the outer tube 1 at points P1 and P1 ′, and the inner tube 2 and the outer tube 1 are integrally expanded, and the end point P2 thereof. And the point P3 is reached. The expansion of the integral pipe expands at the point P3 where the plastic deformation exceeds the elastic limit of the inner pipe steel material for the inner pipe 2 and has a pipe expansion stress of σ1, and the outer pipe 2 The tube expansion is stopped at the point P2 of the expansion progression within the elastic limit of the steel material, and has a tube expansion stress of σ2. Next, at the start of the final fifth stage, the supply of high-pressure water for pipe expansion is immediately stopped, the pressure P applied to the inner surface of the inner pipe 2 is released, and the drainage electromagnetic valve of the drainage port 19 of the slide head 11 is released. 20 is opened, and cooling water is supplied from the cooling water pump 24 to the water channel 17 through the pipe 42 via the check valve 25. Therefore, the double tube in which the inner tube 1 and the outer tube 2 are integrally fitted is cooled and thermally contracted, the diameter is reduced, and residual stress is generated on the fitting surfaces of both tubes.

  That is, cooling contraction stops at points P4 and P6 shown in FIG. 6 to form a double pipe, and residual stresses S1 and S2 are generated on the fitting surfaces of the inner pipe 2 and the outer pipe 1. The residual stress is a double stress having a predetermined fitting force with a tensile stress S1 from point P5 to point P4 on the outer tube 1 and a compressive stress S2 from point P5 to point P6 on the inner tube 2 as a fitting stress. It becomes a tube.

For example, the fitting stress in the double pipe production example of the present invention was a good value with an average of 16.8 kg / mm ² . This is because the steel type of the outer tube: L-80 (radius 44.95 mm, thickness 4.95 mm), the steel type of the inner tube: SAF 2206 (radius 39.5 mm, thickness 1.5 mm), the length of the outer tube and the inner tube The production conditions are as follows: tube expansion time: about 1.0 second, tube expansion pressure: 880 kg / cm ² , outer tube heating temperature: 357 ° C., tube expansion stress: σ1 = 101 kg / mm ² , σ2 = 36. It was 8 kg / mm ² . In addition, the measurement method of a fitting stress is implemented based on API specification 5LD (3rd edition 2009.3) including the Example mentioned later, and the average value of 2 sheets per ring (circumference 180 degree pitch). It is.

(8) Water tightness water pressure test regarding the performance and quality of the double tube The double tube water pressure test C5 shown in the flowchart of FIG. 1 will be described.
After completing the cooling process of the double pipe in the previous section, the drain electromagnetic valve 20 is closed, and high-pressure water for water pressure test (for example, pressurization setting 25.0 MPa) is supplied to the supply port of the ram 3 by the same control as at the start of pipe expansion. The water pressure test is performed by passing water through 15 for a predetermined time (for example, 10 seconds).

(9) Removal of the double tube The heating furnace moving carriage 64 is driven to pull the heating furnace 60 fitted in the basic process C back to the position of the gantry 65, and the mandrel 4 is provided with the inward flare 73 and the outward direction 74. Then, both ends of the pipe portion in the double pipe that is watertight and fixed are opened, and the double pipe is taken out from the mandrel 4. The double pipe moves to the end finishing C4 shown in FIG.

(10) Continuous operation of one system of cooling water supply / discharge system and three lines of manufacturing equipment Using FIG. 8 and Table 1, one system of cooling water supply / discharge system and the double pipe manufacturing apparatus of the present invention Production equipment line 1 (hereinafter referred to as line 1; similarly referred to as lines 2 and 3), line 2 and line 3 are integrated into an integrated facility, so-called “one water supply / drainage system and multi-manufacturing equipment” The example which operates and manufactures a double tube is demonstrated.

  The manufacturing apparatus shown in FIG. 8 uses a system for supplying and draining water by a control device (not shown) to supply necessary cooling water or high-pressure water to three manufacturing apparatus lines in accordance with the progress of the manufacturing process of each manufacturing line. It is a device that supplies and drains in a timely manner. Table 1 shows a time chart in which the production line of the production apparatus shown in FIG. 8 is divided in the order of operation of the process and the required time (minutes) of each process is taken on the horizontal axis. Operate and operate to increase productivity.

  As shown in Table 1, after starting preparations for starting the production apparatus line 1, the process proceeds to pressurization of the accumulator 36, and then proceeds to the insertion of the inner tube 2 and the seal of the flares 73, 74. Start preparation after a minute, and line 1, 2 and 3 after line 3 starts preparation after 60 minutes enter operation state. One supply / discharge system such as cooling water controls cooling water and high pressure water Based on the signal of the equipment, the valves of the related branching devices 87, 88 and 89 and the electromagnetic valve are opened and closed to supply and discharge the necessary cooling water, and the high pressure water for expansion is controlled so as not to overlap with other lines. And supply.

  Line 1 that started production first completes the production of the double pipe after an elapsed time of 1 hour and 42 minutes (total operation time for each process: 2 hours and 10 minutes (130 minutes)). The line 1 starts to insert the second inner pipe 2 with a time lag of 8 minutes, and the production proceeds in the same manner as the first one.

  In the present invention, the manufacturing apparatus line 1 to the manufacturing apparatus line 3 can be successively operated in accordance with the time chart shown in Table 1, so that the productivity is extremely high, and the process work of the outer pipe 1 in the process of one line. Since it can be carried out in parallel with other steps, the cycle time can be shortened, and the present invention can produce 6 double tubes after 4 hours shown in Table 1.

  Next, the reasons for limiting the numerical values, the effects, and the like of the present invention will be described in the manufacturing method and manufacturing apparatus described in the above embodiments (1) to (10).

[The preferable heating temperature of the outer tube 1 is 100 ° C. to 500 ° C.]
The preferable heating temperature of the outer tube 1 is 500 ° C. or less because the outer tube 1 mainly made of carbon steel is tempered by a manufacturing company of the outer tube in the final process of manufacture, and has a quality such as an arbitrary standard. This is because if the temperature of the tempered steel material is set to a temperature that does not alter the temperature, and the temperature exceeds 500 ° C., the yield point of the outer tube steel material is lowered and the tensile strength may be lowered. On the other hand, if the temperature is less than 100 ° C, the outer tube 1 has little thermal expansion and may not reach the target inner diameter. If the temperature is less than 100 ° C, the inner surface of the steel tube has moisture due to condensation, etc., and remains between the fitting surfaces. There is a risk of deteriorating the quality. Therefore, the preferable heating temperature of the outer tube 1 is set to 100 ° C to 500 ° C.

[Preferable temperature of cooling water is 30 ° C. or less]
The lower the temperature of the inner tube 2, that is, the greater the temperature difference from the outer tube 1, the higher the fitting stress. Therefore, when the heated outer tube 1 is relatively layered so as to cover the inner tube 2, water having a temperature as low as possible is supplied as cooling water to prevent the temperature of the inner tube 2 from rising. Further, immediately before the start of the pipe expansion, the drainage electromagnetic valve 20 is closed and the cooling water in the high-pressure water chamber 17 is in a sealed state. Therefore, as low a cooling water as possible is necessary to maintain the low temperature of the inner pipe 1. . In addition, immediately after the expansion of the pipes at points P2 and P3 shown in FIG. 6, in order to immediately cool the double pipe rapidly and in large quantities, a large amount of cooling water is passed to cool the double pipe to 100 ° C. or lower. From this point of view, in order to efficiently produce a double pipe having a uniform and predetermined fitting stress, the cooling water is preferably 30 ° C. or lower, and 10 ° C. or lower in order to increase the cooling capacity and increase the productivity. For example, it is more preferable to supply at 5 ° C.

[Preferable tube expansion time is 0.5 to 5 seconds]
If the tube expansion time is long, the temperature of the outer tube 1 decreases, the temperature of the inner tube 1 increases, the temperature difference between the inner tube 1 and the outer tube 2 decreases, and the contraction of the outer tube 1 in the fifth stage. Since the amount is reduced, the fitting stress is lowered, so that the tube expansion time is preferably as short as possible. However, if the tube expansion time is less than 0.5 seconds, the uniform pressure / arrow P cannot be applied over the entire length of the high-pressure water chamber 17, and there is a possibility that uniform tube expansion cannot be performed. On the other hand, if it exceeds 5 seconds, the temperature difference between the inner tube 2 and the outer tube 1 becomes small, and it takes time for cooling in the fifth stage, and there is a possibility that an appropriate and uniform fitting stress cannot be obtained. Therefore, the tube expansion time is preferably 0.5 seconds to 5 seconds.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.
Table 2 shows the component system of the outer steel pipe 1 used in Examples and Comparative Examples of the present invention, its component examples, and applicable standards for reference.

    Table 3 shows examples of main components and applicable standards of the inner steel pipe used in the examples and comparative examples of the present invention.

  Table 4 shows the sizes and manufacturing conditions of the outer steel pipe and the inner steel pipe of Examples and Comparative Examples of the present invention.

  Table 5 shows the situation at the time of pipe expansion, the hydraulic pressure test, the production results, and the evaluation of the double pipe in the examples and comparative examples of the present invention.

No. shown in Table 4 and Table 5. Nos. 1 to 13 are examples of the present invention that satisfy the requirements of the present invention, and were good products with no uniform fitting stress and product shape defects of appropriate values in the manufactured double pipe. However, no. 8 and no. In No. 13, the heating temperature of the outer tube was slightly lower, so the amount of heat shrinkage was small, and the fitting stress was within the standard value but slightly lower. In addition, the fitting stress value between the outer steel pipe and the inner steel pipe in the double pipe of the present invention was set to 10 kg / mm ² or more as a satisfactory value satisfying the API standard.

  On the other hand, no. 14 and no. 15 is a comparative example that does not employ an axial force guarantee cylinder. The mandrel does not respond to the contraction pressure in the axial direction during tube expansion, the slide head travel is large, the fitting stress varies, and the inner tube is seated. Bending or bending occurred in the double pipe, and the shape inspection failed.

The double pipe manufacturing method and the double pipe manufacturing apparatus of the present invention are mainly used for sour gas transport line pipes, oil well pipes, and chemical plant steel pipes for chemical plants in which the outer steel pipe is carbon steel and the inner steel pipe is corrosion-resistant steel pipe. It can be used to produce high quality double pipes with high productivity.

DESCRIPTION OF SYMBOLS 1 Outer pipe, outer steel pipe 2 Inner pipe, inner steel pipe 3 Ram 4 Mandrel 5 Seal disk 6 Mandrel tip 7 Clamping nut 8 8 'Fixed frame 9 Moving beam 10 Connecting rod 11 Slide head 12 Axial force compensation cylinder 13 Compensation cylinder piston 14 Compensation cylinder high-pressure water receiving port 15 Cooling water, high-pressure water supply port 16 Cooling water passage or high-pressure water passage 16 (a) Water passage (a)
16 (b) Waterway (b)
17 Water passage or high-pressure water chamber 18 Seal jaw 19 Cooling water, high-pressure water drain 20 Drain electromagnetic valve 21 21 'Drain pipe 22 Water storage tank 23 Cooling water supply valve 24 Cooling water supply pump 25 Check valve 26 Booster water supply electromagnetic valve 27 Check valve 28 Booster water supply pipe 29 29'29 "Cooling water supply check valve 30 Booster 31 Secondary cylinder c chamber 32 Secondary cylinder b chamber 33 Secondary cylinder a chamber 34 Hydraulic solenoid valve 35 Hydraulic unit
36 accumulator 37 hydraulic pipe 38 hydraulic electromagnetic valve 39 39'39 "piston 40 40 '40" high pressure water supply electromagnetic valve 41 41' 41 "high pressure water supply pipe 42, 42 'cooling water supply pipe
43 Primary side cylinder chamber 44 44 '44 "High pressure water check valve 45 Motor valve 46 Main pressurizing valve I' Cooling water flow direction
B High-pressure water flow direction C Ha 'High-pressure oil flow direction D Drainage flow direction 50 Mandrel support device 51 Elevating air cylinder 52 Heating furnace traveling rail 53 Support member tilting direction 54 Base 60 Heating furnace 61 Exhaust damper 62 Thermometer 63 Gas burner 64 Heating Reactor moving carriage 65
66 Rotary chuck 67 Rotary chuck moving motor 68 Chain 69 Heating furnace moving motor 70 Rotary chuck moving direction 71 Heating furnace moving direction
A Basic process A: Cooling water supply, high-pressure oil circulation system and booster B Basic process B: Axial force compensation cylinder, ram, mandrel base C Basic process C: Fitting of slide head tip, mandrel, inner tube and outer tube D Basic process D: Outer tube heating furnace, outer tube rotating device and their carriage, outer tube heating, movement 72 Watertight seal 73 Inward flare 74 Outward flare dp Inner diameter when inner tube is inscribed in outer tube by expansion dr Slide head ram diameter dc Slide head cylinder diameter dt Slide head cone throat (narrowest) inner diameter dm Mandrel diameter Fr Rightward axial force (inner tube compression)
Fl Leftward axial force (inner tube tension)
D _PO initial pipe inner diameter D _LO inner pipe initial outer diameter P radial water pressure P1 P1 'contact point of inner pipe outer surface with inner pipe inner surface P2 outer pipe expansion stop, thermal contraction start point σ2 outer Pipe expansion stress P3 Inner pipe expansion stop, thermal contraction start point σ1 Inner pipe expansion stress P4 Outer pipe thermal contraction completion point P5 Pipe tensile stress and compressive stress branch point P6 Inner pipe thermal contraction completion point 75 Fire resistance Brick 76-1 Side wall refractory material 76-2 Ceiling refractory material 77 Roll support shaft 78 Steel pipe axis adjustment jig
79 Steel tube rotating roll 80 Furnace side wall 81 Furnace opening / closing frame 82 Hydraulic cylinder 83 Furnace opening / closing rod 84 Furnace rotation shaft 85 Furnace opening / closing direction 87 Branch 1
88 turnout 2
89 Branch 3
101 Outer tube 102 Coil heater 103 Inner tube 104 Inner 105 Perforated plug body 105 ′ Plug body 106 Hole 107 Liquid supply direction 108 Pressurizing direction 201 Outer tube 202 Inner tube 203 203 ′ Inner tube tip flare, base flare 205 Fixing ram
206 206′206 ″ Seal head 207 Conical tapered surface 208 Seal jaw 209 Tie rod (FIG. 3)
210 Fixed seal head 211 Expanded pipe flow path 212 Drainage path 214 Flow path 215 Double pipe manufacturing device 216 Stand 217 Core metal 218 Hydraulic cylinder 219 219 ′ Piston rod 220 Seal 221 Expanded chamber 223 External path 224 224 ′ Oil path 225 Nut 228 External cylinder
F tube expansion pressure

Claims (9)

The outer steel pipe is thermally expanded in advance, the inner steel pipe is relatively overlaid on the outer steel pipe, the inner steel pipe is hydraulically expanded and brought into contact with the inner surface of the outer steel pipe, the outer steel pipe is cooled and contracted, and both the steel pipes are tightly fitted. In the double pipe manufacturing method,
When the inner steel pipe is hydraulically expanded, an axial force in a direction that compensates for the hydraulic axial force generated by the hydraulic expansion of the inner steel pipe is applied to the slide head that is slidable in the axial direction while supporting the inner steel pipe. And adjusting the axial force balance.   The double pipe manufacturing method according to claim 1, wherein the outer steel pipe is heated to 100 to 500 ° C. and thermally expanded in advance.   The double pipe manufacturing method according to claim 1 or 2, wherein the inner steel pipe is cooled with cooling water of 30 ° C or lower when the inner steel pipe is relatively layered on the outer steel pipe.   The supply stage of the high-pressure water when the inner steel pipe is expanded with water is set to two or more stages, and the time until the high-pressure water reaches a predetermined maximum pressure in the final stage is 0.5 to 5 seconds. The double pipe manufacturing method in any one.   The inner steel pipe and the outer steel pipe are tightly fitted to form a double pipe, and then a water pressure test of the double pipe is performed by supplying high-pressure water to a water passage when the inner steel pipe is hydraulically expanded. The double pipe manufacturing method in any one. The outer steel pipe is thermally expanded in advance, the inner steel pipe is relatively overlaid on the outer steel pipe, the inner steel pipe is hydraulically expanded and brought into contact with the inner surface of the outer steel pipe, the outer steel pipe is cooled and contracted, and both the steel pipes are tightly fitted. In double pipe manufacturing equipment,
An axial force compensation cylinder that adjusts the axial force balance by adding an axial force in a direction that compensates for the hydraulic axial force generated by the hydraulic expansion of the inner steel pipe to a slide head that supports the inner steel pipe and is slidable in the axial direction. A double pipe manufacturing apparatus characterized by being provided.   The double pipe manufacturing apparatus according to claim 6, further comprising a water supply / drainage mechanism that supplies or drains cooling water or high-pressure water to the slide head and the axial force compensation cylinder.   The double-pipe manufacturing apparatus according to claim 7, wherein the water supply / drainage mechanism includes a booster that receives water from a water supply tank and receives high-pressure oil from an oil circulation system to supply high-pressure water.   The double pipe manufacturing apparatus according to claim 8, wherein the booster includes a plurality of stages.

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