Method for connecting pipes in high-pressure resin pipe joints

Abstract

Traditionally, the main reciprocating transport pipes through which chilled and hot water circulates have been sealed piping systems using steel pipes (such as white pipes or internally lined steel pipes). However, due to the relative installation locations of the main transport pipes and air conditioning equipment, bending points are required when connecting the pipes. This posed a problem when using steel pipes, as it necessitated the use of elbows and flexible joints. [Solution] A high-pressure resistant resin pipe with an outer cross-linked polyethylene layer thickness of 1.5 mm and an inner cross-linked polyethylene layer thickness of 3.55 mm is used as the attached pipe, joined to a high-pressure resistant fitting, and used to connect the reciprocating transport main pipe and the air conditioning equipment (fan coil unit).

Description

Technical Field

[0001] The present invention relates to a method for connecting pipes at a joint of a high-pressure-resistant joint and a high-pressure-resistant resin pipe as a connecting pipe used for connecting a reciprocating conveyance main pipe and air-conditioning equipment (fan coil unit).

Background Art

[0002] Conventionally, a reciprocating conveyance main pipe through which cold and warm water circulates has been a closed piping system, and steel pipes (such as white pipes and internally lined steel pipes) have been used. However, due to the relationship between the installation positions of the reciprocating conveyance main pipe and the air-conditioning equipment, a bending portion is required during pipe connection. Therefore, when connecting with a steel pipe, an elbow or a flexible joint is required. Furthermore, the generation of rust due to dissolved oxygen in the circulating water becomes a problem.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The invention described in the patent document uses a resin pipe having flexibility and oxygen permeation prevention performance as a connecting pipe member for connecting a reciprocating conveyance main pipe and air-conditioning equipment. As a result, elbows and flexible joints are not required, and the piping itself is lighter than a steel pipe or an aluminum three-layer pipe, so workability is improved. Since it is a one-touch connection where the pipe is simply inserted into the joint, special tools are not required and construction workability is improved.

[0005] However, in the case of the invention described in the patent document, if the same resin pipe is used in parts with different set pressures, there is a risk of the pipe bursting or breaking. Due to the load in the direction that pulls the pipe out of the joint, the stopper member of the joint bites into the surface of the resin pipe, and because the adhesive surface from the end face of the resin pipe to the stopper biting position is small, delamination of the interface between the cross-linked polyethylene layer and the adhesive layer occurs due to insufficient adhesive strength, which may cause the resin pipe to come out of the joint. [Means for solving the problem]

[0006] This invention aims to address the above-mentioned problems, and improves pressure resistance by increasing the pipe thickness compared to existing resin pipes, resulting in a high-pressure resistant resin pipe. Specifically, for a nominal diameter of 16A, the outer diameter remains unchanged at 27.0 mm, while the pipe thickness is increased from 2.65 mm to 5.25 mm.

[0007] The fitting has been improved from the current model by increasing the number of stopper biting blades (biting parts) from one to two. This distributes the load that acts in the direction of the pipe coming out of the fitting, improving long-term reliability while maintaining pull-out prevention force.

[0008] As a result, the thickness of the outer cross-linked polyethylene layer was set to 1.5 mm in the high-pressure resistant resin pipe to reduce the risk of delamination at the interface between the cross-linked polyethylene layer and the adhesive layer without compromising the oxygen permeability prevention performance.

[0009] By making the thickness of the outer cross-linked polyethylene layer 1.5 mm, the stopper does not reach the outer adhesive layer, allowing for a gap of approximately 1 mm between the stopper blade and the outer adhesive layer. As shown in Figure 3, this reduces the risk of delamination at the interface between the cross-linked polyethylene layer and the adhesive layer.

[0010] Specifically, as shown in Figure 3, the current 0.2 mm outer cross-linked polyethylene layer is increased to 1.5 mm, and the 2.25 mm inner cross-linked polyethylene layer is increased to 3.55 mm. Additionally, as shown in Figure 4, the length from the end face of the pipe to the stopper engagement point is increased by approximately 1.5 times, thereby increasing the adhesive surface area and suppressing the pipe from coming loose from the joint. [Brief explanation of the drawing]

[0011] [Figure 1] This diagram illustrates an embodiment of the present invention, showing the connection relationship between the reciprocating main pipe of the heat source unit and the air conditioning equipment. [Figure 2] Similarly, this is a front view of a longitudinal cross-section of a joint, showing a connection structure between a high-pressure joint and a high-pressure resin pipe as connecting piping according to an embodiment of the present invention. [Figure 3] Similarly, this is an enlarged longitudinal cross-sectional front view illustrating an embodiment of the present invention, showing the connection structure between a high-pressure joint and a high-pressure resin pipe, specifically the portion where the high-pressure resin pipe and the stopper engage. [Figure 4] Similarly, this is a comparative drawing of longitudinal cross-sectional front views of a conventional product and an embodiment of the present invention, showing the length to which the insertion length of the resin pipe according to the present invention can be changed. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described below with reference to the drawings. In the schematic diagram of Figure 1, 1 is a high-pressure joint that connects a supply main pipe 12, which supplies and transports a heat transfer medium from a heat source unit (not shown) to an air conditioning unit 11, and a return main pipe 13, which returns the heat-exchanged medium from the air conditioning unit 11 to the heat source unit, via a connecting pipe 14.

[0013] Figure 2 shows the connection structure of a high-pressure fitting 1 and a high-pressure resin pipe 2 as connecting piping 14. The primary side of the high-pressure fitting 1 is the body 7 that connects to the air conditioning equipment 11 or the reciprocating transport main pipes 12 and 13 to be connected, and the secondary side is the insertion joint for the high-pressure resin pipe.

[0014] The high-pressure resistant resin pipe 2 is inserted through the inner core 3 into the insertion joint of the high-pressure resistant fitting equipped with an O-ring 4, and is secured by the cap 6 via the stopper 5.

[0015] Furthermore, the stopper 5 is equipped with two cutting blades 51 and 52 to distribute the load that acts in the direction of pulling the pipe out of the joint, thereby improving long-term reliability while maintaining the pull-out prevention force.

[0016] In the past, there was a risk that the stopper 5 would bite into the vicinity of the interface between the inner-layer crosslinked polyethylene layer and the inner-layer adhesive layer, causing delamination of the interface of the inner-layer adhesive layer. In the resin tube 2 for high pressure resistance of the present invention, in order to reduce the risk of delamination of the interface between the crosslinked polyethylene layer and the adhesive layer without impairing the oxygen barrier performance, the thickness of the outer-layer crosslinked polyethylene layer is set to 1.5 mm. By setting the thickness of the outer-layer crosslinked polyethylene layer to 1.5 mm, the stopper cannot reach the outer-layer adhesive layer, and a gap of about 1 mm can be provided between the tip of the stopper blade and the outer-layer adhesive layer, reducing the risk of delamination of the interface between the outer-layer crosslinked polyethylene layer and the adhesive layer.

[0017] Also, as shown in FIG. 4, the adhesive surface is increased by about 1.5 times the length from the end face of the tube to the position where the stopper bites in. By setting the length from the end face of the tube to the position where the stopper bites in to 25.2 mm, the volume of the adhesive layer is increased, and by increasing the volume of the adhesive layer, further extraction from the joint is suppressed.

Industrial Applicability

[0018] The pipe connection method in the high-pressure-resistant resin pipe joint according to the present invention can improve the long-term reliability while maintaining the extraction prevention force when used as a connection pipe for connecting the reciprocating conveyance main pipe and the air-conditioning equipment, and has extremely high industrial applicability in the pipe equipment industry.

Explanation of Signs

[0019] 1 High-pressure-resistant joint 11 Air-conditioning equipment 12 Forward conveyance main pipe 13 Return conveyance main pipe 14 Connection pipe 2 High-pressure-resistant resin pipe 3 In-core of high-pressure-resistant joint 4 O-ring of high-pressure-resistant joint 5 Stopper of high-pressure-resistant joint 51, 52 Biting blades of high-pressure-resistant joint stopper 6 Cap of high-pressure-resistant joint 7 Body of high-pressure-resistant joint

Claims

1. A piping connection method used for connecting a reciprocating transport main pipe and air conditioning equipment, in which a high-pressure resistant resin pipe with an outer cross-linked polyethylene layer thickness of 1.5 mm or more is used as the attached pipe and joined to a high-pressure resistant fitting.

2. A high-pressure joint consisting of a shell on the primary side that connects to the air conditioning equipment or reciprocating transport main pipe, and a secondary side that serves as an insertion joint for a high-pressure resistant resin pipe.

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