JPH07317975A - End section corrosion preventive structure for flanged composit tube - Google Patents

Abstract

PURPOSE:To provide the end section corrosion preventive structure far a flanged composit tube which can assure stable corrosion resistance even under a severe usage condition allowing hot and cold water to pass through. CONSTITUTION:A flange fitting 3 is installed onto a duplex tube 2 having a resin layer 22 in the inner surface of a metallic tube 21, the cylindrical section 11 of a short tube A made of resin, which has a brim section 12 at its cylindrical section 11, is inserted into the tube end section of a duplex tube with a flange via a packing 4 where the end of the resin layer is positioned at the end of a metallic tube, or the cylindrical section 11 of the short tube A made of resin, which has the brim section 12 at its cylindrical section 11, and also has a rubber layer at the outer circumference of the cylindrical section, is inserted therein with the rubber layer compressed, and the brim section 12 of the short tube A is bonded onto the flange fitting 3 at the end of the duplex tube with adhesives 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pipe end anticorrosion structure for a flanged composite pipe in which a flange fitting is attached to the pipe end of the composite pipe having a resin layer on the inner surface of the metal pipe.

[0002]

2. Description of the Related Art When a metal pipe is used as a fluid transport pipe, an inner surface anticorrosion treatment is required. A composite pipe in which an extruded resin pipe is adhered to the inner surface of the metal pipe with an adhesive, and a metal strip are vertically aligned. There is known a composite pipe or the like in which a tubular inner surface is extrusion-coated with a resin while welding in a tubular form having eyes.

In the connection of such a composite pipe, if the fluid in the pipe comes into contact with the end of the resin layer, the fluid enters the interface between the resin layer and the metal pipe from the end of the resin layer to cause interface separation. There is a fear of developing, especially in hot water flow pipes, the danger is great, and waterproof treatment for the resin layer end is essential.

Conventionally, when the above-mentioned composite pipe is flange-connected, as shown in FIG. 5, a composite pipe 2 '(2 in FIG.
1'is a metal tube, 22 'is a resin layer) A screw groove 31' is cut on the outer surface of the end of the metal tube, a flange metal fitting 3'is screwed into the screw groove 31 ', and a flange is provided at one end of the tubular portion 11'. The tubular portion 11 ′ of the resin short pipe A ′ having the portion 12 ′ is adhered to the inner surface of the resin layer of the composite pipe 2 ′ with the adhesive 51 ′, and the flange portion 12 ′ is adhered to the inner surface of the flange fitting 3 ′ with the adhesive 52 ′. By each,
Next, a structure in which the flange fittings of both composite pipes are fastened together with a flange pressing fitting and a bolt via a packing, or as shown in FIG. 6, a flange fitting 3'is welded to the metal pipe end of the composite pipe 2 '(32 'And 33' indicate a welded portion), the resin layer portion deteriorated by welding heat is removed, and the resin short pipe A'is extended from the inner surface side of the flange metal fitting 3'to the resin layer stripping end portion 220 '. Adhesive (51 "is an adhesive between the resin layer 22 'and the resin short pipe A', 52" is an exposed inner surface 210 'of the metal pipe and between the flange metal fitting 3'and the resin short pipe A'. Adhesive) is used for bonding, and then the flange fittings of both composite pipes are fastened with flange holding fittings and bolts through packing (Japanese Utility Model Publication No. 61-74385).

[0005]

However, according to the test results of the present inventors regarding the flange connection structure of these composite pipes, under the cold / hot water flow condition in which hot water flow and cold water flow are alternately repeated, It is unavoidable that the interface between the resin layer on the inner surface of the pipe and the tubular portion of the short pipe made of resin prematurely peels off, or cracks occur at the root of the collar portion of the short pipe made of resin.

The cause of this is that the resin layer of the composite pipe has a shrinkage force in the lengthwise direction caused by heating due to the orientation of the resin molecular chains and the residual stress at the time of extrusion, and the collar portion of the resin short pipe is In the state of being fixed to the flange fitting at the end of the composite pipe, each time of heating, the tubular portion of the short pipe is stretched and bending stress repeatedly occurs at the root of the collar to cause fatigue fracture of the root of the collar, or
It is presumed that a shearing force acts on the adhesive interface between the resin layer and the short tubular portion each time heating is performed, and the interface is sheared and fractured.

It is an object of the present invention to provide an end anticorrosion structure for a flanged composite pipe which can ensure stable anticorrosion even under severe conditions such as cold and hot water flow.

[0008]

According to the present invention, there is provided an end anticorrosive structure for a flanged composite pipe, wherein a flange metal fitting is attached to a pipe end of the composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is a metal pipe. Inside the pipe end portion of the flanged composite pipe located at the end, the tubular portion of the resin short pipe having the flange portion at one end of the tubular portion is inserted through packing, or the flange portion is provided at one end of the tubular portion. The tubular portion of a resin short tube having a rubber layer on the outer circumference of the tubular portion is inserted under compression of the rubber layer, and the collar portion of the short tube is attached to the flange metal fitting of the composite pipe end by an adhesive. The structure is characterized by being bonded.

According to another structure of the flanged composite pipe of the present invention, a flange fitting is attached to the pipe end of the composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is deeper than the metal pipe end. Inside the pipe end of the flanged composite pipe, the rubber layer or the metal pipe end is covered over the resin layer end, and the rubber layer is covered to cover the resin layer and the flange metal fitting. Is injection-molded.

As the above-mentioned composite pipe, for example, a heat-expandable resin pipe (for example, made of vinyl chloride resin) that expands by heating due to a memory effect is applied, and an adhesive (for example, hot-melt adhesive) is applied to the outer surface. After being inserted into a metal pipe (eg, steel pipe, aluminum pipe, etc.), the heat-expandable resin pipe is expanded by heating from outside the metal pipe and adhered to the inner surface of the metal pipe, ordinary resin Pipe (made of vinyl chloride resin, for example)
After applying an adhesive (eg, adhesive) to the outer surface, insert it into a metal pipe (eg, steel pipe, aluminum pipe, etc.), sink the metal pipe with a roll die, etc. Welded to the tubular body having a joint in the longitudinal direction, and an L-shaped resin extrusion die is inserted into the tubular body from the upstream side of the welded portion, and the resin discharged from the die is A welded tubular body coated on its inner surface (for example, JP-A-3-227218) is used.

The structure of the end anticorrosion structure of the flanged composite pipe according to the present invention will be described below with reference to the drawings. FIG. 1A is an explanatory view showing an example of the resin short pipe A used in the invention of claim 1, which is made of a synthetic resin such as heat-resistant vinyl chloride resin and has one end of the tubular portion 11. On the collar part 12
The rubber ring mounting groove 13 is formed on the outer surface of the tubular portion 11, and the reinforcing metal ring 14 is embedded in the thickness of the groove 13.

FIG. 1B is an explanatory view showing an embodiment of the invention described in claim 1. In FIG. 1B, 2 is a composite pipe, which has a resin layer 22 on the inner surface of the metal pipe 21. 3 is a flange metal fitting attached to the end of the composite pipe, and a screw groove 31 is cut on the outer surface of the metal pipe end of the composite pipe,
The flange fitting 3 is screwed into the screw groove 31, and spot welding or punching is performed to prevent the flange fitting 3 from rotating. Inner surface 33 of this flange fitting 3
And the end face 23 of the composite pipe 2 are flush with each other, and an inner corner 24 at the end of the composite pipe is provided with an arm (usually 2 to 5R). A is a short tube made of resin described above, and after the rubber ring 4 is mounted in the rubber ring mounting groove 13, the tubular portion 11 is inserted into the tube end portion of the composite tube 2, and the tubular portion 11 and the composite tube 2 are joined together. A rubber ring 4 seals between the resin layer 22 and an adhesive 5 seals between the flange 3 and the flange 12.

This adhesive 5 is a contact between a metal member (flange metal fitting) and a resin member (resin short tube) whose adhesive interface has a different thermal expansion coefficient, and the thermal stress acting on the interface is applied. To alleviate, it is preferable to use a rubber adhesive. Further, for this adhesion, the adhesive 5 is applied to the inner side surface 33 of the flange metal fitting 3 of the composite pipe and the outer side surface 120 of the flange portion 12 of the resin short pipe A, respectively, as shown in FIG. A method of pressing the collar portion 12 of the resin short pipe A to the flange metal fitting 3 at the end of the composite pipe with the pressing plate 6 can be used. In this case, the front surface side of the pressing plate 6 or the rear surface side of the flange metal fitting 3 can be pressed. -The adhesive effect of the adhesive 5 can be rapidly exhibited by heating with a solder or the like.

FIG. 2A is an explanatory view showing an embodiment of the invention described in claim 2. Instead of using the rubber ring 4 in the embodiment shown in FIG. As shown in (b), the rubber layer 41 is previously integrally provided on the outer surface of the tubular portion 11 of the resin short tube main body a, and as shown in FIG. The portion 11 is inserted into the pipe end portion of the composite pipe 2 under the compression of the rubber layer 41, and the adhesive 5 is provided between the flange portion 12 of the short pipe A and the flange metal fitting 3 at the composite pipe end in the same manner as above.
Adhered by. In addition, also in (a) of FIG.
Similar to FIG. 1B, the flange metal fitting 3 is attached to the end of the composite pipe by screwing, and the inner corner 24 of the end of the composite pipe is provided with an arm (usually 2 to 7R).

In contrast to the above, as shown in FIG. 3, the rubber layer 4
1 is not only the outer circumference of the tubular portion 11 of the resin short pipe A but also the collar portion 12.
Can be fixed over the outer surface of the flange. In this case, in the state of flange connection, the rubber layer portion 410 between the flange metal fitting 3 and the collar portion 12 of the resin short pipe A is compressed by the tightening force of the bolt and is sealed. Because it exhibits the property, (a) in Fig. 2
The adhesive can be omitted by the adhesive 5 between the collar portion of the short pipe and the flange metal fitting at the end of the composite pipe.

FIG. 4A shows an embodiment of the invention according to claim 4, in which the flange fitting 3 is attached to the end of the metal pipe of the composite pipe 2 by welding 32, 33. Two
3 is welded to the flange 3 and the flange 33 is welded (usually 2 to 7R), the resin layer portion that has been heated by the welding heat is removed, and the resin layer end 220 is deeper than the metal pipe end. Is located in. Reference numeral 7 denotes a rubber layer covering the end of the metal tube and covering the end of the resin layer. The rubber short tube 7 (whether foamed or solid) shown in FIG. An adhesive 5, for example, a rubber-based adhesive is applied to the outer surface of the rubber short tube 7 and the composite tube side portion to which the rubber short tube is applied, and then applied. 8 is a rubber layer 7
Is a resin cover that is injection-molded to cover the resin layer 22 and the flange metal fitting 3, and the composite pipe end is set in an injection mold, and the same resin as the resin layer 21 is injection-molded. I am doing it.

In the flanged composite pipe with pipe end corrosion protection according to the present invention, the plate-like packing is sandwiched between the flange fittings, the flange fittings are fitted between the flange fittings, and the flange fittings are fastened with bolts. , Connected by normal flange connection method.

[0018]

When the composite pipe 2 is heated by circulating hot water,
In the resin layer 21, the orientation and residual stress of the resin molecular chains, which have been frozen until then, at the time of extrusion molding are released, and the resin layer 21 tends to contract in the length direction.

Therefore, in FIG. 1B, the resin layer 2
Even if 2 contracts in the length direction, in the rubber ring 4,
The original packing action is exhibited under the relative sliding with the surface to be sealed, and the intrusion of water into the resin layer end e from between the tubular portion 11 of the resin short tube A and the resin layer 22 is prevented by the rubber. The packing action of the ring 4 prevents the water from entering the resin layer end e from between the flange fitting 3 and the flange 12 of the resin short pipe A by the adhesive 5.

Further, the contraction force generated in the resin layer 22 is absorbed by the sliding between the rubber ring 4 and the resin layer 22, and the bending deformation at the collar root b of the resin short tube A is sufficiently suppressed. Thus, even under repeated heating, early bending fatigue fracture of the resin short tube A is prevented.

Therefore, stable waterproofing against the resin layer edge e is achieved despite the lengthwise shrinkage of the resin layer 22. In (a) of FIG. 2 as well, since the rubber layer 41 on the outer circumference of the tubular portion 11 of the resin short tube A performs a good packing action like the rubber ring, stable water stoppage against the resin layer end e is It is achieved despite the lengthwise shrinkage of the resin layer 22.

In FIG. 4A, the resin cover 8 is formed by injection molding, and the cover 8 and the resin layer 22 are welded and firmly integrated during the injection molding. When the resin layer 22 contracts in the lengthwise direction, a shearing force acts on the interface between the resin cover 8 and the resin layer 22, but since this interface is welded and integrated, interfacial peeling does not occur. To be prevented. Further, the contraction force in the length direction of the resin layer 22 is transmitted to the resin cover 8, but the stress generated in the resin cover 8 due to the elasticity of the rubber layer 7 is sufficiently relaxed (the rubber layer 7 is absent. However, when the resin cover 8 is in contact with the metal pipe, stress relaxation at the resin cover cannot be expected, and stress concentration particularly occurs at the portion in contact with the end of the metal pipe), and stable water stoppage at the resin layer end is obtained. , Despite the lengthwise shrinkage of the resin layer 22.

[0023]

EXAMPLES In the following examples and comparative examples, a composite pipe having a nominal diameter of 100 A, in which a metal pipe is a steel pipe and a resin layer is a hard vinyl chloride resin pipe, is used.

[Embodiment 1] In FIG. 1B, a pipe taper screw 31 (JIS B) is attached to the outer periphery of the metal pipe end of the composite pipe.
0203) is cut, the flange metal fitting 3 is screwed, and further,
A punch stop was applied. The radius of attachment of the metal tube end 24 was 4 mm. The resin short tube A is an injection-molded product of heat-resistant hard vinyl chloride resin, the thickness of the tubular portion 11 is 5 mm, the outer diameter of the tubular portion 11 is 96.5 mm, the depth of the rubber ring mounting groove 13 is 2 mm, The flange 12 had a thickness of 4 mm and the flange 12 had an outer diameter of 144 mm. The rubber ring 4 was an O-ring having a diameter of 3 mm and a rubber hardness of 70. A futile rubber adhesive was used as the adhesive 5 for bonding the flange portion 12 of the resin short pipe A and the flange metal fitting 3 of the flanged composite pipe.

[Embodiment 2] In FIG. 2A, a short tube A made of resin has a thickness of a cylindrical portion 11 of 2 mm, an outer diameter of the cylindrical portion 11 of 93.8 mm, and a thickness of a flange portion 4 of 4 mm. A heat-resistant hard vinyl chloride resin injection-molded product body a having an outer diameter of 144 mm and a rubber layer 41 having a thickness of 2 mm and a rubber hardness of 70 provided on the outer surface of the cylinder was used. Same as above.

[Embodiment 3] In FIG. 4A, after the flange metal fitting 3 is welded to the outer periphery of the metal pipe end portion of the composite pipe,
The resin layer was removed from the pipe end over a length of 70 mm with a luter grinder, and the welded portion 33 between the metal pipe end face 23 and the flange fitting 3 was halved at a radius of 5 mm. The short rubber tube 7 has a small-diameter tubular portion having a length of 20 mm and an outer diameter of 97.
5 mm, the length of the large diameter tubular portion is 69 mm, and the outer diameter is 105.
5mm, thickness of cylinder is 2mm, outer diameter of collar is 144m
butyl rubber adhesive is used as the adhesive 5 applied to the outer surface of the rubber short pipe 7 and the composite pipe side portion to which the rubber short pipe is adhered. It was used. Further, a hard vinyl chloride resin of the same material as the resin layer 22 of the composite pipe 2 was used as the resin of the resin cover 8, and injection molding was performed at about 190 ° C.

[Comparative Example 1] In FIG. 5, a flange metal fitting 3'was screwed and fixed to the outer periphery of the metal pipe end portion of the composite pipe in the same manner as in Example 1. The resin short pipe A'is an injection-molded product of heat-resistant hard vinyl chloride resin, and the thickness of the tubular portion 11 'is 4
mm, the outer diameter of the tubular portion 11 'is 98 mm, the thickness of the collar portion 12' is 4 mm, and the outer diameter of the collar portion 12 'is 144 mm. The resin layer 22' of the tubular portion 11 'and the composite pipe 2'is used. Adhesion with 5
A vinyl chloride adhesive for water pipes was used for 1 ', and a butyl rubber adhesive was used for bonding 52' between the flange 12 'and the flange fitting 3'of the composite pipe.

[Comparative Example 2] In Fig. 6, a flange metal fitting 3'was welded to the outer periphery of the metal pipe end portion of the composite pipe in the same manner as in Example 3, and then a resin layer was laid from the pipe end to a length of 70 mm with a router. -It was removed by a grinder, and the welded portion 33 'at the end of the metal tube was taken with a radius of 5 mm. Resin short tube A '
Has a small-diameter tubular portion with a length of 30 mm and an outer diameter of 98 mm,
The diameter of the large diameter cylinder is 69 mm, and the outer diameter is 105.3 mm,
Using a heat-resistant hard vinyl chloride resin injection-molded product having a cylindrical portion with a thickness of 4 mm, a flange portion with an outer diameter of 144 mm, and a thickness of 4 mm. Butyl rubber adhesive is used for adhesion 52 "between the flange and the flange of the composite pipe, and PVC 51 for water pipes is used for adhesion 51" between the small tubular part of the resin short pipe and the resin layer of the composite pipe. Adhesives were used respectively.

For each of these example products and comparative example products, 5 pieces were flange-connected, and a cold / hot water test was conducted in which hot water at 80 ° C. for 5 minutes and normal temperature water for 5 minutes made one cycle. As a result, in Comparative Examples 1 and 2, 30
Before the 00 cycle, peeling of the adhesive interface between the resin short tube and the resin layer of the composite tube or cracks at the collar root of the resin short tube occurred, but in Examples 1 to 3, 600
Even after the lapse of 0 cycles, no abnormality was observed in all the connection parts.

[0030]

According to the present invention, when a flange metal fitting is attached to the pipe end of a composite pipe having a resin layer on the inner surface of a metal pipe and the composite pipes are flange-connected to each other, cold water flow and hot water flow are repeated. Even under such severe operating conditions, water resistance against the resin layer end inside the pipe end can be stably maintained, and combined with the use of a resin layer with excellent heat resistance, a highly reliable heat resistant composite pipe Piping can be installed.

[Brief description of drawings]

FIG. 1 (a) is an explanatory view showing an example of a resin short tube used in the invention according to claim 1, and FIG. 1 (b) is an explanatory view showing an embodiment of the present invention, FIG. 1C is an explanatory view showing an assembled state of the embodiment.

FIG. 2A is an explanatory view showing an embodiment of the invention described in claim 2, and FIG. 2B is an explanatory view showing a resin short pipe used in the embodiment. is there.

FIG. 3 is an explanatory diagram showing an embodiment of the invention described in claim 3;

FIG. 4 (a) is an explanatory view showing an embodiment of the invention described in claim 4, and FIG. 4 (b) is an explanatory view showing a rubber short pipe used in the same embodiment. is there.

FIG. 5 is an explanatory diagram showing a conventional example.

FIG. 6 is an explanatory diagram showing another conventional example different from the above.

[Explanation of symbols]

 A resin short pipe 11 cylinder part 12 collar part 13 rubber ring mounting groove 2 composite pipe 21 metal tube 22 resin layer 3 flange metal fitting 31 screw groove 32 welding part 33 welding part 4 rubber ring 41 rubber layer 5 adhesive 7 rubber layer 8 Resin cover

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F16L 58/18

Claims (4)

[Claims] 1. A flange fitting is attached to a pipe end of a composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is located at the metal pipe end. With a flange characterized in that the tubular portion of a resin-made short pipe having a flange at one end is inserted through a packing, and the flange of the short pipe is bonded to a flange metal fitting at the end of the composite pipe with an adhesive. Anticorrosion structure at the end of the composite pipe. 2. A flange fitting is attached to the pipe end of a composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is located at the metal pipe end. A resin short tube having a flange at one end and a rubber layer on the outer circumference of the tube is inserted under compression of the rubber layer, and the flange of the short tube is a flange metal fitting at the end of the composite tube. An end-corrosion preventive structure for a flanged composite pipe, characterized in that it is adhered to the end with an adhesive. 3. A flange fitting is attached to a pipe end of a composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is located at the metal pipe end. Corrosion protection at the end of a flanged composite pipe in which the tubular part of a resin short pipe having a collar part at one end and a rubber layer on the outer circumference of the tubular part and the outer surface of the flange part is inserted under compression of the rubber layer Construction. 4. A flange metal fitting is attached to the pipe end of a composite pipe having a resin layer on the inner surface of the metal pipe, and the resin layer end is located inside the pipe end of the flanged composite pipe. A flanged composite pipe characterized in that a rubber layer or a metal pipe is covered over the resin layer end portion, and the resin layer and the flange metal fitting are covered by injection molding to cover the rubber layer. Corrosion-proof structure at the end.