Device and method for testing sealing performance of water-cooled metal pipe joint

Abstract

The invention relates to the technical field of motor manufacturing and testing, and discloses a device and method for testing the sealing performance of a water-cooled metal pipe joint, and the device comprises a polytetrafluoroethylene plastic pipe, a three-way joint, two first elbows, and movable joints disposed at the two ends of the polytetrafluoroethylene plastic pipe. The ends, close to the polytetrafluoroethylene plastic pipe, of the two first elbows are each provided with a fixed connector. According to the device and the method for testing the sealing performance of the water-cooled metal pipe joint, a polytetrafluoroethylene plastic pipe, two first elbows, two first connecting pipes, two second elbows, a second connecting pipe, a third connecting pipe, a three-way joint, a transition joint and an internal and external thread movable joint are mounted, and all the parts are tightened to form a closed loop; vPI (vacuum pressure impregnation) insulating paint whole immersion and high-temperature baking processes are strictly completed, and whether the sealing performance of the cooling metal pipe joint and the polytetrafluoroethylene plastic pipe is qualified and effective or not can be judged according to a test result through a water pressure resistance test.

Description

Technical Field

[0001] The invention relates to the technical field of motor manufacturing and testing, and in particular to a device and method for testing the sealing performance of a water-cooled metal pipe joint. Background Art

[0002] In motor cooling structures, water is widely used as a cooling medium due to its large heat capacity, low viscosity, good fluidity, and excellent thermal conductivity. Common non-magnetic tooth superconducting synchronous motors have four drawn rectangular hollow water-cooling copper tubes inserted into each stator coil. The heat generated by the stator coils is carried away by the water in the hollow water-cooling copper tubes, resulting in significant heat dissipation. The superconducting synchronous motor stator uses a structure where the hollow water-cooling copper tubes in the coils are connected to fixed metal pipe joints, which are then sealed to a polytetrafluoroethylene (PTFE) tube. This structure is similar to the metal pipe joint and PTFE tube sealing connection structure of steam turbine generator water-cooled stators. This connection structure has been widely used in steam turbine generator stator water cooling systems. In steam turbine generators, the metal pipe joints and PTFE tubes are installed and connected naturally at room temperature, without undergoing high-temperature baking of the motor. A leak-proof hydrostatic test is sufficient. This structure is well-established in steam turbine generators, and its installation and sealing verification are completed at room temperature without undergoing an insulation treatment process.

[0003] However, the stator of a superconducting synchronous motor must undergo VPI (Vacuum Pressure Impregnating), a process involving vacuum pressure impregnation and baking at 170°C ± 5°C for 12-20 hours. During this process, differences in thermal expansion coefficients between the metal joints and the plastic tube, as well as the softening of the polytetrafluoroethylene material at high temperatures, can lead to seal failure after cooling. Existing technologies have the following drawbacks:

[0004] The room-temperature sealing experience of steam turbine generators cannot be directly transferred to the high-temperature manufacturing scenario of superconducting motors. Direct testing on product motors is high-risk and costly, and reliability verification cannot be completed before mass production. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention provides a device and method for testing the sealing performance of a water-cooled metal pipe joint, which solves the problems mentioned in the above background.

[0006] The present invention provides the following technical solution: a device and method for testing the sealing performance of a water-cooled metal pipe joint, comprising: a polytetrafluoroethylene plastic pipe, a tee joint, two first elbows, and flexible joints provided at both ends of the polytetrafluoroethylene plastic pipe;

[0007] The two first elbows are each provided with a fixed joint at one end close to the polytetrafluoroethylene plastic tube, one end of the fixed joint is threadedly connected to the inner wall of the flexible joint, and a copper sealing gasket is provided at the interface between the fixed joint and the flexible joint. The two first elbows are each connected to a first connecting pipe at one end away from the polytetrafluoroethylene plastic tube, and a second elbow is installed at the top end of the two first connecting pipes, one end of the second elbow is connected to the second connecting pipe, and the other end of the second elbow is connected to the third connecting pipe, the tee joint is installed at one end of the second connecting pipe, and the other two ends of the tee joint are respectively provided with a transition joint and an inner and outer thread flexible joint, and the inner and outer thread flexible joint is connected to one end of the third connecting pipe.

[0008] Preferably, the flexible joint includes a flexible hexagonal copper joint, a pipe joint core shaft and a cylinder, one end of the pipe joint core shaft passes through the flexible hexagonal copper joint and is inserted into the interior of the cylinder, the end of the polytetrafluoroethylene plastic tube is inserted between the joint pipe joint core shaft and the cylinder, and a compression mold is used to radially compress the cylinder, and the cylinder and the pipe joint core shaft clamp the tube wall of the polytetrafluoroethylene plastic tube to achieve a sealed connection.

[0009] Preferably, both ends of the first connecting pipe, the second connecting pipe and the third connecting pipe are provided with tapered pipe threads, and the ends of the transition joints and the surfaces of the tapered pipe threads are wrapped with 8-10 layers of polytetrafluoroethylene sealing tape.

[0010] Preferably, the fixed joint is a stainless steel joint, and the fixed joint is connected to the first elbow by copper brazing.

[0011] Preferably, the inner and outer thread flexible joint (11) includes an outer tap seat flexible joint, an inner tap seat flexible joint and a locking hexagonal nut, the outer tap seat flexible joint is connected to one end of the tee joint (9), the inner tap seat flexible joint is connected to one end of the third connecting pipe, the locking hexagonal nut is connected to the outer circle of the inner tap seat flexible joint, and the outer thread of the end of the outer tap seat flexible joint is connected to the thread of the end of the locking hexagonal nut, and a sealing rubber gasket is provided between the end face of the outer tap seat flexible joint and the end face of the inner tap seat flexible joint.

[0012] Preferably, a connecting pipe is installed at the end of the transition joint, and one end of the connecting pipe is connected to a water pump.

[0013] A method for testing the sealing performance of a water-cooled metal pipe joint comprises the following steps:

[0014] Step S1: Assemble the test device by sequentially installing the polytetrafluoroethylene plastic tube, two first elbows, two first connecting pipes, two second elbows, a second connecting pipe, a third connecting pipe, a tee joint, a transition joint, and an internal and external threaded joint, and tightening each component to form a closed circuit;

[0015] Step S2: Process simulation: After all components of the water-cooled metal pipe joint sealing performance test device are connected, a connecting pipe is installed on the transition joint, and the pipe joint test device is fixed to the motor stator wire. The preheating, VPI vacuum pressure impregnation and baking process flow is carried out together.

[0016] Step S3: Step water pressure test: connect the water pump through the connecting pipe to perform water pressure test.

[0017] Preferably, in step S2, when the water-cooled metal pipe joint sealing performance test device is immersed in insulating paint under VPI vacuum pressure, an isobaric immersion method is adopted. When the water-cooled metal pipe joint sealing performance test device is completely immersed in the insulating paint solution, the connecting pipe on the water-cooled metal pipe joint sealing performance test device extends out of the insulating paint liquid surface, so that the pressure outside and inside the device are the same, thereby maintaining the pressure balance inside and outside the device.

[0018] Preferably, in step S3, the actual test parameters are first selected as 1 MPa, 30 min, which has the highest technical requirements;

[0019] If there is no leakage, the test time will be extended by 30 minutes;

[0020] If there is no leakage, the test time will be extended for another 60 minutes;

[0021] If there is no leakage, the test time will be extended for another 120 minutes;

[0022] The final test value is: 1MPa, 240min, no leakage is judged as qualified.

[0023] Preferably, before step S3, a pre-test step is added: an airtightness test at 0.5 MPa for 30 minutes is performed before and after VPI immersion in paint.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention comprises the following steps: installing a polytetrafluoroethylene plastic tube, two first elbows, two first connecting tubes, two second elbows, a second connecting tube, a third connecting tube, a tee joint, a transition joint, and an internal and external threaded flexible joint; tightening the components to form a closed loop; strictly completing the VPI whole-dipping insulating paint and high-temperature baking processes; and undergoing a water pressure test. Based on the test results, it is possible to determine whether the sealing performance of the cooling metal pipe joint and the polytetrafluoroethylene plastic tube is qualified and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the structure of the polytetrafluoroethylene plastic tube and the flexible joint of the present invention;

[0027] Figure 2This is a schematic structural diagram of the first elbow and the fixed joint of the present invention;

[0028] Figure 3 This is a schematic structural diagram of the first connecting pipe, the second connecting pipe and the third connecting pipe of the present invention;

[0029] Figure 4 This is a schematic diagram of the installation structure of the first elbow and the polytetrafluoroethylene plastic tube of the present invention;

[0030] Figure 5 It is a schematic diagram of a partial side cross-section of the docking structure of a fixed joint and a flexible joint of the present invention;

[0031] Figure 6 This is a schematic diagram of the installation structure of the first connecting pipe of the present invention;

[0032] Figure 7 This is a schematic structural diagram of the second elbow, second connecting pipe, third connecting pipe and tee joint of the present invention;

[0033] Figure 8 This is a schematic diagram of the installation structure of the internal and external thread joint of the present invention;

[0034] Figure 9 This is a schematic diagram of the installation structure of the transition joint of the present invention;

[0035] Figure 10 This is a schematic diagram of the connecting pipe installation structure of the present invention;

[0036] Figure 11 It is a schematic diagram of the water pump docking structure of the present invention.

[0037] In the figure: 1. PTFE plastic tube; 2. flexible joint; 21. flexible hexagonal copper joint; 22. pipe joint mandrel; 23. cylinder; 3. first elbow; 4. fixed joint; 5. first connecting pipe; 6. second elbow; 7. second connecting pipe; 8. third connecting pipe; 9. tee joint; 10. transition joint; 11. internal and external thread flexible joint; 111. external tap seat flexible joint; 112. internal tap seat flexible joint; 113. locking hexagonal nut; 114. sealing rubber gasket; 12. copper sealing gasket; 13. tapered pipe thread; 14. connecting pipe; 15. VPI varnish dipping tank; 16. motor stator wire embedding; 17. water pump. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] See also Figure 1-11 A device and method for testing the sealing performance of a water-cooled metal pipe joint includes: a polytetrafluoroethylene plastic pipe 1, a tee joint 9, two first elbows 3, and flexible joints 2 provided at both ends of the polytetrafluoroethylene plastic pipe 1;

[0040] The two first elbows 3 are each provided with a fixed joint 4 at one end close to the polytetrafluoroethylene plastic tube 1, one end of the fixed joint 4 is threadedly connected to the inner wall of the flexible joint 2, and a copper sealing gasket 12 is provided at the interface between the fixed joint 4 and the flexible joint 2, the two first elbows 3 are each connected to a first connecting pipe 5 at one end away from the polytetrafluoroethylene plastic tube 1, and a second elbow 6 is installed at the top of the two first connecting pipes 5, one end of the second elbow 6 is connected to the second connecting pipe 7, and the other end of the second elbow 6 is connected to the third connecting pipe 8, a tee joint 9 is installed at one end of the second connecting pipe 7, and the other two ends of the tee joint 9 are respectively provided with a transition joint 10 and an inner and outer thread flexible joint 11, and the inner and outer thread flexible joint 11 is connected to one end of the third connecting pipe 8.

[0041] The flexible joint 2 includes a flexible hexagonal copper joint 21, a pipe joint spindle 22 and a cylinder 23. One end of the pipe joint spindle 22 passes through the flexible hexagonal copper joint 21 and is inserted into the inside of the cylinder 23. The end of the polytetrafluoroethylene plastic tube 1 is inserted between the joint pipe joint spindle 22 and the cylinder 23. A compression mold is used to radially compress the cylinder 23. The cylinder 23 and the pipe joint spindle 22 clamp the tube wall of the polytetrafluoroethylene plastic tube 1 to achieve a sealed connection. The polytetrafluoroethylene plastic tube 1 adopts a special sealing treatment. Specifically, the polytetrafluoroethylene plastic tube 1 joint is placed in the compression mold, and the cylinder 23 is pressurized. The outer circle of the cylinder 23 is compressed and deformed, so that the cylinder 23, the polytetrafluoroethylene plastic tube 1 and the spindle are tightly connected to meet the sealing requirements.

[0042] Both ends of the first connecting pipe 5 , the second connecting pipe 7 and the third connecting pipe 8 are provided with tapered pipe threads 13 , and the end of the transition joint 10 and the surface of the tapered pipe threads 13 are wrapped with 8-10 layers of polytetrafluoroethylene sealing tape.

[0043] The fixed joint 4 is a stainless steel joint, and the fixed joint 4 is connected to the first elbow 3 by copper brazing.

[0044] The internal and external thread flexible joint 11 includes an external tap seat flexible joint 111, an internal tap seat flexible joint 112 and a locking hexagonal nut 113. The external tap seat flexible joint 111 is connected to one end of the tee joint 9, the internal tap seat flexible joint 112 is connected to one end of the third connecting pipe 8, the locking hexagonal nut 113 is connected to the outer circle of the internal tap seat flexible joint 112, and the external thread at the end of the external tap seat flexible joint 111 is connected to the thread at the end of the locking hexagonal nut 113. A sealing rubber gasket 114 is provided between the end face of the external tap seat flexible joint 111 and the end face of the internal tap seat flexible joint 112.

[0045] A connecting pipe 14 is installed at the end of the transition joint 10 , and one end of the connecting pipe 14 is connected to a water pump 17 .

[0046] A method for testing the sealing performance of a water-cooled metal pipe joint comprises the following steps:

[0047] Step S1: Assemble the test device by sequentially installing the polytetrafluoroethylene plastic tube 1, two first elbows 3, two first connecting pipes 5, two second elbows 6, second connecting pipe 7, third connecting pipe 8, tee joint 9, transition joint 10, and internal and external thread joint 11, and tightening all components to form a closed circuit;

[0048] Step S2: Process simulation: After all components of the water-cooled metal pipe joint sealing performance test device are connected, the connecting pipe 14 is installed on the transition joint 10, and the pipe joint test device is fixed to the motor stator wire 16, and then flows into the preheating, VPI vacuum pressure impregnation and baking process.

[0049] Step S3: Step water pressure test: connect the water pump 17 via the connecting pipe 14 to perform a water pressure test.

[0050] In step S2, when the water-cooled metal pipe joint sealing performance test device is immersed in insulating paint under VPI vacuum pressure, an isobaric immersion method is adopted. When the water-cooled metal pipe joint sealing performance test device is completely immersed in the insulating paint solution, the connecting pipe 14 on the water-cooled metal pipe joint sealing performance test device extends out of the insulating paint liquid surface, so that the pressure outside and inside the device are the same, maintaining the pressure balance inside and outside the device.

[0051] In step S3, the actual test parameters are first selected as 1 MPa, 30 min, which has the highest technical requirements;

[0052] If there is no leakage, the test time will be extended by 30 minutes;

[0053] If there is no leakage, the test time will be extended for another 60 minutes;

[0054] If there is no leakage, the test time will be extended for another 120 minutes;

[0055] The final test value is: 1MPa, 240min, no leakage is judged as qualified.

[0056] Before step S3, a pre-test step is added: an airtightness test at 0.5 MPa for 30 minutes is performed before and after VPI immersion.

[0057] First, a flexible joint 2 is installed at each end of the polytetrafluoroethylene plastic tube 1, wherein one end of each of the two first elbows 3 is connected to a fixed joint 4, and the first elbow 3 and the fixed joint 4 are connected by copper brazing. The outer circles of the first connecting pipe 5, the second connecting pipe 7 and the third connecting pipe 8 are processed with tapered pipe threads 13 for connection, and copper sealing washers 12 are placed inside the flexible hexagonal copper joints 21 at both ends of the polytetrafluoroethylene plastic tube 1. Then, the flexible hexagonal copper joints 21 at both ends of the polytetrafluoroethylene plastic tube 1 are connected to the fixed joint 4 on the first elbow 3 using their own threads. The tapered pipe thread 13 of the first connecting pipe 5 is wrapped with 8 to 10 layers of polytetrafluoroethylene sealing tape, and then screwed into the internal thread hole of the first elbow 3 and connected together using their own threads. The second elbow 6 is screwed onto the two first connecting pipes 5 respectively, and the tapered pipe threads 1 of the second connecting pipe 7 and the third connecting pipe 8 are 3 Wrap 8 to 10 layers of polytetrafluoroethylene sealing tape and screw them into the second elbow 6 respectively. The end of the second connecting pipe 7 is screwed into the tee joint 9, and then the outer tap seat joint 111 is installed at the right end of the tee joint 9. The locking hexagonal nut 113 is sleeved on the outer circle of the inner tap seat joint 112. The inner tap seat joint 112 is installed at the left end of the third connecting pipe 8. The connecting end surfaces of the outer tap seat joint 111 and the inner tap seat joint 112 are padded with sealing rubber gaskets 114, and the inner tap seat joint 112 is screwed into the outer tap seat joint 111 and tightened. In this way, a closed pipeline space is formed. Wrap 8 to 10 layers of polytetrafluoroethylene sealing tape on the external thread of the transition joint 10, and then screw the transition joint 10 into the threaded hole of the tee joint 9 to complete the installation of the pipe joint sealing test device. Connect the connecting pipe 14 of the water pump 17 at one end of the transition joint 10 to carry out the water pressure test.

[0058] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A water-cooled metal pipe joint sealing performance test device, characterized in that: include: A polytetrafluoroethylene plastic tube (1), a three-way joint (9), two first elbows (3), and flexible joints (2) provided at both ends of the polytetrafluoroethylene plastic tube (1); The two first elbows (3) are each provided with a fixed joint (4) at one end close to the polytetrafluoroethylene plastic tube (1), one end of the fixed joint (4) is threadedly connected to the inner wall of the flexible joint (2), and a copper sealing gasket (12) is provided at the interface between the fixed joint (4) and the flexible joint (2), the two first elbows (3) are each connected to a first connecting pipe (5) at one end away from the polytetrafluoroethylene plastic tube (1), and the top ends of the two first connecting pipes (5) are each installed with a second elbow (6), the end of one of the second elbows (6) is connected to the second connecting pipe (7), and the end of the other second elbow (6) is connected to the third connecting pipe (8), the three-way joint (9) is installed at one end of the second connecting pipe (7), and the other two ends of the three-way joint (9) are respectively installed with a transition joint (10) and an inner and outer thread flexible joint (11), and the inner and outer thread flexible joint (11) is connected to one end of the third connecting pipe (8).

2. A water-cooled metal pipe joint sealing performance test device according to claim 1, characterized in that: The flexible joint (2) comprises a flexible hexagonal copper joint (21), a pipe joint mandrel (22) and a cylinder (23); one end of the pipe joint mandrel (22) passes through the flexible hexagonal copper joint (21) and is inserted into the interior of the cylinder (23); the end of the polytetrafluoroethylene plastic tube (1) is inserted between the joint pipe joint mandrel (22) and the cylinder (23); a pressing die is used to radially compress the cylinder (23); the cylinder (23) and the pipe joint mandrel (22) clamp the tube wall of the polytetrafluoroethylene plastic tube (1) to achieve a sealed connection.

3. A water-cooled metal pipe joint sealing performance test device according to claim 1, characterized in that: Both ends of the first connecting pipe (5), the second connecting pipe (7) and the third connecting pipe (8) are provided with tapered pipe threads (13), and the end of the transition joint (10) and the surface of the tapered pipe threads (13) are wrapped with 8-10 layers of polytetrafluoroethylene sealing tape.

4. A water-cooled metal pipe joint sealing performance test device according to claim 1, characterized in that: The fixed joint (4) is a stainless steel joint, and the fixed joint (4) is connected to the first elbow (3) by copper brazing.

5. The water-cooling metal pipe joint sealing performance test device according to claim 1, characterized in that: The inner and outer thread flexible joint (11) comprises an outer tap seat flexible joint (111), an inner tap seat flexible joint (112) and a locking hexagonal nut (113); the outer tap seat flexible joint (111) is connected to one end of the tee joint (9); the inner tap seat flexible joint (112) is connected to one end of the third connecting pipe (8); the locking hexagonal nut (113) is connected to the outer circle of the inner tap seat flexible joint (112); the outer thread of the end of the outer tap seat flexible joint (111) is connected to the thread of the end of the locking hexagonal nut (113); and a sealing rubber gasket (114) is provided between the end face of the outer tap seat flexible joint (111) and the end face of the inner tap seat flexible joint (112).

6. A water-cooled metal pipe joint sealing performance test device according to claim 1, characterized in that: A connecting pipe (14) is installed at the end of the transition joint (10), and one end of the connecting pipe is connected to a water pump (17).

7. A method for testing the sealing performance of a water-cooled metal pipe joint, characterized in that: The following steps are involved: Step S1: Assemble the test device, install the polytetrafluoroethylene plastic tube (1), two first elbows (3), two first connecting pipes (5), two second elbows (6), second connecting pipe (7), third connecting pipe (8), tee joint (9), transition joint (10) and internal and external thread joint (11) in sequence, and tighten all components to form a closed circuit; Step S2: Process simulation, after all parts of the water-cooled metal pipe joint sealing performance test device are connected, the connecting pipe (14) is installed on the transition joint (10), and the pipe joint test device is fixed on the motor stator wire (16), and flows into the preheating, VPI vacuum pressure impregnation insulation paint and baking process together; Step S3: Step water pressure test: connect the water pump (17) via the connecting pipe (14) to perform water pressure test.

8. A water-cooling metal pipe joint sealing performance test method according to claim 7, characterized in that: In the step S2, when the water-cooled metal pipe joint sealing performance test device is immersed in the insulating paint under the VPI vacuum pressure, an isobaric immersion method is adopted. When the water-cooled metal pipe joint sealing performance test device is completely immersed in the insulating paint solution, the connecting pipe (14) on the water-cooled metal pipe joint sealing performance test device extends out of the insulating paint liquid surface, so that the pressure outside and inside the device are the same, and the pressure inside and outside the device is kept balanced.

9. A water-cooling metal pipe joint sealing performance test method according to claim 7, characterized in that: In step S3, the actual test parameters are first selected as 1 MPa, 30 min, which has the highest technical requirements; If there is no leakage, the test time will be extended by 30 minutes; If there is no leakage, the test time will be extended for another 60 minutes; If there is no leakage, the test time will be extended for another 120 minutes; The final test value is: 1MPa, 240min, no leakage is judged as qualified.

10. A water-cooling metal pipe joint sealing performance test method according to claim 7, characterized in that: Before step S3, a pre-test step is added: an airtightness test at 0.5 MPa for 30 minutes is performed before and after VPI immersion.

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