Manufacturing method of housing tube and housing tube

Abstract

To easily provide a housing pipe having satisfactory inner and outer surface quality.SOLUTION: A method for producing a housing pipe in which projections 3 are respectively provided at outer circumferential faces in both end parts of a straight pipe part 2 with the same diameter over the whole length, and the respective end parts are connected with other pipes by a housing joint 30 via the projections 3, comprises: a straight pipe part production step of annealing the straight pipe part 2 after being molded by centrifugal casting; a scale removal step of removing a scale formed at a pipe outer face of the straight pipe part 2 by the annealing; a thermal spraying step of performing zinc-based thermal spraying treatment to the pipe outer face of the straight pipe part 2 with the removed scale to form a thermal-sprayed coating 4; and a processing step of cutting the end part of the straight pipe part 2 in which the thermal-sprayed coating 4 is formed to form each projection 3 extending in a circumferential direction of the straight pipe part 2 at the end part.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a housing tube and a housing tube for connection by a housing joint. [Background technology]

[0002] For example, as shown in FIG. 5, a fire extinguishing system is installed in a tunnel T of a highway in preparation for a fire in the tunnel T. This fire extinguishing system is composed of fire hydrant devices A installed at predetermined intervals along the length of the tunnel, and water supply piping P for supplying water to the fire hydrant devices A. The water supply piping P is formed by connecting a housing tube 1' with a housing joint 30. A T-shaped branch pipe B is connected to the water supply piping P at a position corresponding to the fire hydrant devices A, and water is supplied to the fire hydrant devices A through this T-shaped branch pipe. When a fire breaks out in the tunnel T, initial fire extinguishing can be performed by spraying water from the fire hydrant devices A near the fire site.

[0003] As shown in FIG. 6, this water supply pipe P may be installed at a high point on the inner wall of the tunnel T. The top of this inner wall is often arched, and the beam F of the crane that hoists the pipe material may interfere with the arched top, making it difficult to directly suspend the pipe material at the piping position (support protruding beam H). For this reason, it is necessary to install a temporary support beam G corresponding to the piping position, suspend the pipe material on this support beam G once, and then move it to the specified piping position by holding it sideways by rolling or the like. In this case, it is difficult to adopt an insertion type joint structure that requires axial movement of the pipe when connecting the pipe, and a housing pipe that is connected by a housing joint that minimizes axial movement when connecting the pipe, as shown in Patent Document 1 below, is often adopted.

[0004] The housing pipe 1' may be a cast pipe cast by centrifugal casting. A centrifugal casting machine used for this centrifugal casting method is shown in FIG. 7. This centrifugal casting machine rotates a cylindrical mold 20 as a casting mold by rollers 21, sends molten metal m to a casting trough 24 via ladles 22 and 23, and casts the molten metal m into the cylindrical mold 20, which moves back and forth in the axial direction while rotating around its axis, via the casting trough 24. Then, by the centrifugal force generated by the rotation of the cylindrical mold 20, the molten metal m is uniformly distributed on the inner surface of the cylindrical mold 20, and a cast pipe 25 with a uniform pipe thickness can be cast.

[0005] As shown in the figure, most cast pipes 25 cast by this centrifugal casting method have a receiving port 25a with a bulge formed at one end and an insertion port 25b at the other end that is inserted into the receiving port 25a. The bulge of the receiving port 25a is formed by loading a core 26 into the cylindrical mold 20. In addition, mold bands 27, 28 are provided at both ends of the cylindrical mold 20 to prevent leakage of molten metal m from these ends. The cast pipe 25 is demolded by removing the mold band 28 on the receiving port 25a side, and then pulling the cast pipe 25 out of the cylindrical mold 20 with the core 26 still attached by hooking the claws of a puller on the inner surface of the receiving port 25a.

[0006] The housing tube 1' can be manufactured, for example, by the process shown in Fig. 8. To give an overview of this process, first, a tube is cast (step S20) using a centrifugal casting machine or the like shown in Fig. 7, and then annealed (step S21). As shown in Fig. 7, this tube has a shape having a socket 25a at one end and an insertion port 25b at the other end that is inserted into the socket 25a.

[0007] Following this annealing, the following processes (flow 1) are performed: descaling (step S22), pipe cutting (step S23), welding and processing of the protrusions at both ends (step S24), and water pressure testing (step S25). The descaling process is a process for removing the oxide scale formed on the surface by annealing. The pipe cutting process is a process for cutting the ends of the cast pipe to a predetermined pipe length. The welding and processing process of the protrusions at both ends is a process for forming protrusions at the ends of the pipe by forming a circumferential groove at the end of the pipe and fitting a ring member therein, or by directly fitting and welding a ring member without forming a circumferential groove, or by grinding a bulge portion formed at the end of the pipe by casting, the outer circumferential surface of which bulges in the radial direction. The water pressure testing process is a process for inspecting the pipe by applying water pressure to the inside after blocking both ends of the pipe.

[0008] Following the series of steps in Flow 1, a step (Flow 2) of inner surface corrosion prevention (step S26) is carried out. The inner surface corrosion prevention step is a step of carrying out mortar lining or powder coating on the inner surface of the pipe.

[0009] Following the process of flow 2, a process of removing red rust (step S27) (flow 3) is performed. The red rust removal process is a process of removing red rust formed on the outer surface of the pipe as a result of undergoing a water pressure test or the like, by blasting.

[0010] Following the process of Flow 3, a process (Flow 4) of exterior painting (Step S28) is performed. The exterior painting process is a process in which a primer such as a zinc-rich primer made of a zinc-based paint as an anti-rust paint is applied to the pipe surface from which the red rust has been removed, and a layer (for example, four layers) of a synthetic resin such as an epoxy resin or a polyurethane resin is further formed on the primer. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] JP 2018-179054 A Summary of the Invention [Problem to be solved by the invention]

[0012] In the process shown in Fig. 8, caps are fitted to both ends of the pipe prior to the red rust removal process to protect the ridges formed on the ends of the pipe from the blast particles used in the red rust removal process and to prevent the blast particles from entering the inside of the pipe. However, the work of protecting the ridges is complicated and time-consuming, and it is difficult to completely prevent the blast particles from entering the inside of the pipe with a cap. This leads to increased costs due to the increased work time, and can cause problems such as the corrosion protection layer on the inner surface being roughened (paint destruction due to collision with blast particles, etc.).

[0013] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to easily provide a housing pipe having good internal and external surface quality. [Means for solving the problem]

[0014] In order to solve the above problems, the present invention provides: A method for manufacturing a housing pipe, in which a straight pipe section having the same diameter over its entire length has ribs on the outer peripheral surfaces of both ends, and each end is connected to another pipe via the ribs by a housing joint, a straight pipe section manufacturing process in which the straight pipe section is formed by centrifugal casting and then annealed; a descaling step of removing scale formed on an outer surface of the straight pipe section by annealing; a thermal spraying step of forming a thermal spray coating on an outer surface of the straight pipe section from which the scale has been removed by performing a zinc-based thermal spraying treatment; a processing step of cutting an end portion of the straight pipe portion on which the thermal spray coating is formed, and forming the protrusion extending in a circumferential direction of the straight pipe portion on the end portion; The present invention provides a method for manufacturing a housing tube, comprising the steps of:

[0015] In this way, if the thermal spraying process is performed immediately after the descaling process to form a thermal spray coating, rust is unlikely to occur on the surface of the tube in the subsequent process, so there is no need to remove red rust by blasting as in the past. In addition, there is no need to fit caps to both ends of the tube to protect the inner surface of the tube prior to the blasting process. This makes it possible to easily manufacture a housing tube with good inner and outer surface quality.

[0016] In the above configuration, The processing process can include each of the following elementary steps: a step of measuring from one end face of the straight pipe portion and cutting the other end face; a step of forming the other protrusion on the outer periphery of the other end face based on the cut other end face; a step of cutting the one end end by measuring from the other end face; and a step of forming one of the protrusions on the one end face based on the cut one end face.

[0017] According to this processing step, the ridges for connecting the housing tubes to each other can be smoothly manufactured in a single operation.

[0018] In each of the above configurations, It is preferable that the method further comprises an anti-rust coating step of applying an anti-rust coating to the outer pipe surface of the straight pipe portion on which the ribs are formed.

[0019] In this way, by applying an anti-rust coating on top of the thermal spray coating, the coating penetrates into the voids in the thermal spray coating, thereby further improving the anti-rust properties of the outer surface of the pipe.

[0020] In the configuration having the anti-rust coating process, It is preferable that an inner surface anticorrosion process is carried out in which the inner surface of the straight pipe section that has been coated with the rust-proofing paint is lined with mortar or powder coated, and an outer surface painting process is carried out in which a synthetic resin paint is applied to the outer surface of the straight pipe section.

[0021] In this way, the water permeability of the pipe can be improved by applying inner surface corrosion protection, and the outer surface coating can increase the durability of the rust prevention and improve the appearance of the pipe.

[0022] In addition, in this invention, A cast housing pipe having a straight pipe section of the same diameter over its entire length, with ribs on the outer circumferential surfaces at both ends, and each end being connected to another pipe via the ribs by a housing joint, The housing pipe is characterized in that a zinc-based spray coating and an anti-rust paint film are formed on the outer surface of the straight pipe section, in that order from the surface, and an inner surface corrosion protection layer made of a mortar lining or powder coating is formed on the inner surface of the straight pipe section.

[0023] As mentioned above, this housing pipe exhibits high rust resistance due to the thermal spray coating and anti-rust paint film formed on the outer surface of the pipe, and high corrosion resistance and water permeability are ensured by the mortar lining or powder coating on the inner surface of the pipe. Effect of the Invention

[0024] According to the present invention, by forming a thermal spray coating on the outer surface of the tube, it is possible to easily provide a housing tube having good inner and outer surface quality. [Brief description of the drawings]

[0025] [Figure 1] 1 shows one embodiment of a housing tube according to the present invention, where (a) is a front view, (b) is a cross-sectional view of a main part of (a), (c) is another example 1 of (b), and (d) is another example 2 of (b). [Diagram 2] 2 shows a manufacturing process for the housing tube shown in FIG. 1. [Diagram 3] FIG. 1 is a cross-sectional view showing an elementary step of the processing process, in which (a) shows the state after the cast pipe has been removed from the cylindrical mold, (b) shows the state after a protrusion has been formed on the other end, and (c) shows the state after a protrusion has been further formed on one end. [Figure 4] Showing the joint of the housing pipe, (a) is a cross-sectional view cut along a plane perpendicular to the pipe axis, and (b) is a cross-sectional view taken along line bb in (a). [Diagram 5] Schematic diagram of fire extinguishing piping in the tunnel [Figure 6] Fire extinguishing piping installation diagram [Figure 7] Schematic diagram of a centrifugal casting machine [Figure 8] FIG. 1 shows a manufacturing process for a housing tube according to the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] A housing pipe 1 according to the present invention will be described with reference to the drawings. As shown in Fig. 1(a), this housing pipe 1 is a cast housing pipe having a straight pipe section 2 of the same diameter over its entire length, and ribs 3 formed on the outer circumferential surfaces of both ends of the straight pipe section 2, and each end of the straight pipe section 2 is connected to another pipe via the ribs 3 by a housing joint 30 (see Figs. 4(a) and 4(b)). On the outer surface of the straight pipe section 2, a thermal spray coating 4, an anti-rust coating film 5, and an outer surface coating film 6 are formed in this order from the surface, and an inner surface anti-corrosion layer 7 is formed on the inner surface of the straight pipe section 2.

[0027] The effective length of the housing pipe 1 can be appropriately selected depending on the application location and use, and can be, for example, 5.2 m (nominal diameter 150 to 250), 6.0 m (nominal diameter 300, 350), etc.

[0028] The straight pipe section 2 is a section of the same diameter obtained by cutting both ends of a cast pipe 8 (see Fig. 3(a)) that has been cast by centrifugal casting and has a socket 8a at one end and a spigot 8b at the other end that is inserted into the socket 8a. Circumferential grooves 9 are formed at both ends of the straight pipe section 2 as shown in Fig. 1(b), and notched rings, which have a notch formed in part of their circumferential direction, are fitted into these circumferential grooves 9. The notched rings are fixed by welding 10 from both axial sides to form the protrusions 3.

[0029] The shape of the protrusion 3 is not limited to the above. For example, as shown in FIG. 1(c), a ring can be directly fitted onto the end of the straight pipe section 2 without forming a circumferential groove, and then fixed from both axial sides by welding 10. Alternatively, as shown in FIG. 1(d), a protrusion 11 can be formed in advance at the casting stage, and the protrusion 3 can be formed by grinding this protrusion 11.

[0030] The sprayed coating 4 is a zinc-based coating formed directly on the outer surface of the straight pipe section 2. In addition to zinc, various alloys containing zinc (e.g., zinc-aluminum alloy) can be used as the "zinc-based" here. The thickness of the coating can be appropriately determined according to the type of sprayed metal and the usage environment of the housing pipe, but the minimum thickness that provides corrosion resistance can be, for example, 20 to 250 μm.

[0031] The anti-rust coating film 5 is a coating film (primer treatment) made of an acrylic resin. By forming this anti-rust coating film 5, the coating film penetrates into the voids on the surface of the zinc-based thermal spray coating 4, further enhancing the anti-rust properties of the thermal spray coating 4. It is possible to use a resin material other than acrylic.

[0032] The outer coating film 6 is a coating film made of a synthetic resin such as an epoxy resin or a polyurethane resin. In Fig. 1(b) to (d), the outer coating film 6 is depicted as a single-layer coating film, but in reality, it is composed of a multi-layer coating film of about 3 to 4 layers. The number of layers can be appropriately changed depending on the type of resin used, the application of the housing pipe 1, etc.

[0033] The inner surface anticorrosive layer 7, which is made of a mortar lining or powder coating, is formed on the inner surface of the pipe with a predetermined thickness. By forming this inner surface anticorrosive layer 7, the inner surface of the pipe becomes smooth, and high water permeability can be ensured.

[0034] The manufacturing process of the housing tube shown in Fig. 1 is shown in Fig. 2. First, a straight tube manufacturing process is performed in which a tube is cast (step S1) using a centrifugal casting machine or the like shown in Fig. 7 and then annealed (step S2). This tube is a cast tube 8 having a receiving port 8a at one end and a spigot 8b at the other end to be inserted into the receiving port 8a, as shown in Fig. 3(a).

[0035] Following annealing, which is carried out in the straight pipe manufacturing process, the following processes (flow 1) are carried out: descaling (step S3), thermal spraying (step S4), pipe cutting (step S5), welding and processing of protrusions at both ends (step S6), hydrostatic testing (step S7), and anti-rust painting of the outer surface (step S8).

[0036] The descaling process is a process for removing oxide scale formed on the outer surface of the tube by annealing, and is carried out, for example, by a blasting method in which hard particles are blasted against the outer surface of the tube at high speed.

[0037] The thermal spraying process is a process of forming a thermal spray coating 4 by performing a zinc-based thermal spraying process on the outer pipe surface of the straight pipe section 2 from which the scale has been removed in the descaling process. As described above, the "zinc-based" used here can be various alloys containing zinc (e.g., zinc-aluminum alloy) in addition to zinc. The thickness of the coating can be appropriately determined depending on the usage environment of the housing pipe 1, and the minimum thickness that provides corrosion resistance can be, for example, 20 to 250 μm.

[0038] The processing step consisting of cutting the pipe and welding and processing the protrusions on both ends is a step consisting of a plurality of elementary steps of cutting the end of the straight pipe section 2 on which the thermal spray coating 4 is formed, and forming the protrusions 3 extending in the circumferential direction of the straight pipe section 2 at the end. An example of this processing step will be described with reference to Figs. 3(a) to 3(c). First, as shown in Fig. 3(a), the straight pipe section 2 is cut along the cutting surface c1 by measuring from the one end face (left end face before cutting) 2a'' (elementary step 1). Next, as shown in Fig. 3(b), the other protrusion 3 is formed on the outer periphery of the other end face 2b based on the cut other end face (right end face after cutting) 2b' (elementary step 2). Furthermore, as shown in Fig. 3(b), the one end face 2a is cut along the cutting surface c2 by measuring from the other end face 2b' (elementary step 3). 3(c), one of the ridges 3 is formed on the one end 2a based on the cut end surface 2a' (elementary process 4). Through this series of elementary processes, the ridges 3 can be formed symmetrically with respect to the center line c in the tube axial direction.

[0039] The water pressure test process is a process in which both ends of the pipe are blocked and water pressure is applied to the inside to perform an inspection. The anti-rust coating process on the exterior is a process in which a paint film (primer treatment) made of acrylic resin is formed. By forming this anti-rust coating film 5, the paint film penetrates into the voids on the surface of the zinc-based sprayed coating 4, further improving the anti-rust properties of this sprayed coating 4. It is possible to use resin materials other than acrylic.

[0040] Following the series of steps in Flow 1, a step (Flow 2) of inner surface corrosion protection (Step S9) is carried out. The inner surface corrosion protection step is a step of forming an inner surface corrosion protection layer 7 of mortar lining or powder coating on the inner surface of the pipe. By carrying out this inner surface corrosion protection, the inner surface of the pipe becomes smooth, and high water permeability can be ensured.

[0041] Following the process of Flow 2, a process (Flow 3) of exterior coating (Step S10) is performed. The exterior coating process is a process of forming an exterior coating film 6 made of a synthetic resin such as an epoxy resin or a polyurethane resin on the outer surface of the pipe on which the anti-rust coating film 5 has been formed. This exterior coating film 6 may be a coating film consisting of a single layer, but is often a coating film consisting of multiple layers, about 3 to 4 layers. The number of layers can be changed as appropriate depending on the type of resin used, the application of the housing pipe 1, etc.

[0042] The housing pipes 1 manufactured in this manner are connected using a housing joint 30, as shown in Fig. 4(a) . This housing joint 30 has a half-annular coupling 31, bolts and nuts 32 that fasten the pair of half-annular couplings 31 at both ends, a rubber ring 33, and an L-shaped fastener 34 provided at the opposing ends of the pair of half-annular couplings 31.

[0043] For this connection, first, a rubber ring 33 is provided at the connection portion of the housing pipes 1 to be connected, as shown in Figure 4(b). Next, a pair of half-annular couplings 31 are fitted to the housing pipes 1 so as to sandwich the ridges 3 formed on the ends of both housing pipes 1 and so that the rubber rings 33 are pressed toward the axial center of the housing pipe 1. Then, when the bolts and nuts 32 (see Figure 4(a)) provided on the half-annular couplings 31 are tightened, both housing pipes 1 are connected watertightly.

[0044] As described above, in the manufacturing method of the housing tube 1 according to the present invention, the thermal spraying process is performed immediately after the scale removal process to improve the corrosion resistance of the outer surface of the tube, eliminating the need for a red rust removal process before the outer surface painting, and also eliminating the need for a primer treatment in the outer surface painting process. In addition, because the red rust removal process is no longer necessary, the task of fitting a protective cap to the end of the tube prior to the red rust removal process is also no longer necessary, and the problem of the inner surface of the tube becoming rough is also solved. This makes it possible to easily manufacture the housing tube 1 with good quality of the inner and outer surfaces.

[0045] Furthermore, the housing pipe 1 according to the present invention is characterized in that it uses the cast pipe 8, which is a casting (ductile cast iron) as described above. Because it is made of casting, it is possible to mass-produce fixed-length pipes by centrifugal casting and to effectively apply mortar lining or powder coating to the inner surface of the pipe. It is also possible to form the protrusions 3 by casting. And by using this fixed-length pipe as a starting material, it is possible to stably and easily manufacture housing pipes of predetermined dimensions.

[0046] The embodiments disclosed herein are illustrative in all respects and should not be considered as limiting. Therefore, the scope of the present invention is defined by the claims, not by the above description, and is intended to include the meaning equivalent to the claims and all modifications. [Explanation of symbols]

[0047] 1 Housing tube 2 Straight pipe section 2a One end side end 2a' (After cutting) one end surface 2a'' (before cutting) One end face 2b Other end 2b' Other end side end surface 3 protrusions 4 Thermal spray coating 5. Anti-rust coating 6. Exterior paint film 7. Inner corrosion protection layer 8 Casting Pipe 8a socket 8b Insertion port 9 Circumferential groove 10. Welding 11 Protrusion 30 Housing joint 31 Semi-circular toroidal coupling 32 Bolts and nuts 33 Rubber Ring 34 L-shaped fastener

Claims

1. A method for manufacturing a housing pipe, comprising the steps of: providing a straight pipe section (2) having the same diameter over its entire length with ribs (3) on the outer peripheral surfaces of both ends thereof; and connecting each end of the straight pipe section (2) to another pipe via the ribs (3) by a housing joint (30), a straight pipe section manufacturing process in which the straight pipe section (2) is formed by centrifugal casting and then annealed; a descaling step of removing scale formed on the outer surface of the straight pipe portion (2) by annealing; a thermal spraying step of performing a zinc-based thermal spraying treatment on the outer surface of the straight pipe section (2) from which the scale has been removed to form a thermal spray coating (4); a processing step of cutting the end of the straight pipe section (2) on which the thermal spray coating (4) is formed, and forming the protrusions (3) extending in the circumferential direction of the straight pipe section (2) at the end; an anti-rust coating process for forming an anti-rust coating film (5) on the outer surface of the straight pipe section (2) on which the protrusions (3) are formed, and for permeating the anti-rust coating film (5) into voids on the surface of the thermal spray coating (4) to perform an anti-rust coating; A method for manufacturing a housing tube, comprising the steps of:

2. 2. The method for manufacturing a housing tube according to claim 1, wherein the processing steps include an elemental step of cutting the other end (2b) by measuring from one end face (2a'') of the straight tube portion (2), an elemental step of forming the other protrusion (3) on the outer periphery of the other end (2b) based on the cut other end face (2b'), an elemental step of cutting the one end (2a) by measuring from the other end face (2b'), and an elemental step of forming one of the protrusions (3) on the one end (2a) based on the cut one end face (2a').

3. 2. The method for manufacturing a housing tube according to claim 1, wherein an inner surface anticorrosion process is performed in which a mortar lining or powder coating is applied to the inner surface of the straight pipe section (2) on which the rust-proofing coating has been applied, and an outer surface painting process is performed in which a synthetic resin coating is applied to the outer surface of the straight pipe section (2) in sequence.

4. A cast housing pipe having a straight pipe section (2) having the same diameter over its entire length and a rib (3) on each of the outer peripheral surfaces at both ends, and each end of the straight pipe section (2) being connected to another pipe via the rib (3) by a housing joint (30), A housing pipe characterized in that a zinc-based thermal spray coating (4) and an anti-rust coating film (5) are formed on the outer surface of the straight pipe section (2) in that order from the surface, the anti-rust coating film (5) permeating into voids on the surface of the thermal spray coating (4), and an inner surface corrosion protection layer (7) made of mortar lining or powder coating is formed on the inner surface of the straight pipe section (2).

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