Pressure resistance test device and test method for metal bellows expansion joints for falling film pipes

Abstract

The invention discloses a pressure resistance test device for a metal bellows expansion joint for a falling film pipe, comprising an outer groove flange and an outer boss flange, and an inner groove flange and an inner boss flange; an outer sealing ring is arranged at the matching position of the outer groove flange and the outer boss flange, and an inner sealing ring is arranged at the matching position of the inner groove flange and the inner boss flange; it also comprises a step screw, one end of the step screw matches the outer groove flange and the outer boss flange, and the other end matches the inner boss flange, and is respectively locked on the steps of the step screw by nuts; the inner groove flange matches the inner boss flange by fixing bolts. The structure of the invention can limit the axial direction of the bellows expansion joint after assembly, and will not cause axial tensile deformation, thereby reducing subsequent shaping work. At the same time, a seal is formed by forcing the sealing ring to produce a large deformation, and the sealing reliability is high. The device can be reused, is convenient and fast, greatly improves production efficiency, and saves production costs.

Description

Technical Field

[0001] The invention relates to the field of inspection equipment for metal bellows expansion joints, in particular to a pressure resistance test device for metal bellows expansion joints used for falling film pipes. Background Art

[0002] Falling film tube is one of the core equipment for producing flake caustic soda. The falling film tube consists of two layers of casing. The material of the jacket layer is molten salt with a maximum working temperature of 430℃; the material of the inner tube layer is alkali solution, and the two liquids are countercurrent for heat transfer. After the alkali solution enters the inner layer of the falling film tube from top to bottom from the distributor, it is heated by the molten salt in the jacket, the alkali solution boils, concentrates and evaporates, and the alkali solution is heated from 164.9℃ liquid alkali solution to 411.9℃ molten alkali. Then it is sent to the gas-liquid separator for separation through the bottom collection pipe. Due to the different media contacted by the inner and outer layers of the falling film tube and different working temperatures, as well as the different materials of the two layers of tubes and the difference in linear expansion coefficients, the deformation amount of thermal expansion and contraction is quite different. The metal bellows expansion joint is installed on the outer layer of the falling film tube, and its own elastic deformation is used to compensate for the difference in deformation of the two layers of casing. For example, the utility model patent with patent number: 201620402992.5 and patent name: "A metal bellows expansion joint for falling film pipe" discloses a metal bellows expansion joint for falling film pipe, including a first pipe, a lining ring, a bellows, and a second pipe. The port of the first pipe is a shrinking structure that matches the outer diameter of the falling film pipe; the number of waves of the bellows is 8 to 10. It significantly improves the service life of the falling film pipe and meets the requirements of the alkali industry for the service life of the falling film pipe.

[0003] According to the requirements, the metal bellows expansion joint for falling film pipes should be subjected to a pressure resistance test before leaving the factory. The test pressure is 0.9MPa, the test medium is water, and the pressure is maintained for 15 minutes. One end of the above expansion joint is the first pipe, and the other end is the second pipe. The raw material specifications of the pipes are 15CrMo with φ133x6. The first pipe is shrunk to φ113 by hot processing. The interface height is about 45mm, and the inner and outer surfaces are non-machined surfaces, with certain rust and out-of-roundness. The bellows has elastic properties and can produce axial compression or tensile displacement under the action of external forces. In the sealed state, when the bellows is subjected to internal pressure, the bellows has a tendency to elongate. When conducting a pressure resistance test, the expansion joint should be limited in the axial direction to prevent the bellows from stretching.

[0004] However, there is currently no better experimental device that can meet the above requirements. Summary of the invention

[0005] The object of the present invention is to provide a pressure resistance test device and a test method for a metal bellows expansion joint for a falling film pipe, which can achieve good sealing and position limitation for the above expansion joint.

[0006] The present invention is achieved through the following technical scheme: a pressure resistance test device for a metal bellows expansion joint for a falling film tube, the bellows expansion joint comprising a first connecting pipe with a shrinkage treatment, a liner ring, a bellows, and a second connecting pipe, characterized in that: the test device comprises an outer groove flange and an outer boss flange matching the outer diameter of the first connecting pipe, and an inner groove flange and an inner boss flange matching the inner diameter of the second connecting pipe; an outer sealing ring is arranged at the matching position of the outer groove flange and the outer boss flange on the outer side of the first connecting pipe, and an inner sealing ring is arranged at the matching position of the inner groove flange and the inner boss flange on the inner side of the second connecting pipe; it also includes a stepped screw, one end of the stepped screw matches the outer groove flange and the outer boss flange, and the other end matches the inner boss flange, and they are respectively locked on the steps of the stepped screw 1 by nuts; the inner groove flange matches the inner boss flange by fixing bolts.

[0007] Furthermore: a test hole connected to the testing machine is arranged on the outer groove flange 3.

[0008] Furthermore: the inner diameters of the outer groove flange 3 and the outer boss flange 5 are slightly larger than the outer diameter of the first connecting pipe; the inner diameter of the outer sealing ring 4 should be slightly smaller than the outer diameter of the first connecting pipe.

[0009] Furthermore, the outer diameters of the inner groove flange 7 and the inner boss flange 9 are slightly smaller than the inner diameter of the second connecting pipe; and the outer diameter of the inner sealing ring 8 is slightly larger than the inner diameter of the second connecting pipe.

[0010] Another solution of the invention is a pressure resistance test method for a metal bellows expansion joint for a falling film tube, using the test device as described above, characterized in that the method comprises the following steps:

[0011] S1. Installation: Install the inner sealing ring into the groove of the inner groove flange, connect the inner boss flange with the inner groove flange and the inner sealing ring with fixing bolts, and keep the inner sealing ring in a loose state to ensure that the inner sealing ring can easily enter the second pipe; insert the step screw into the through hole of the inner boss flange and tighten it with a nut to prevent the step screw from loosening; assemble the second pipe end of the bellows expansion joint to the inner groove flange, and ensure that the end face of the second pipe is in close contact with the inner boss flange, and continue to tighten the fixing bolts until the inner sealing ring is compressed and deformed to form a seal with the inner surface of the second pipe; install the outer boss flange, outer sealing ring and outer groove flange at the first pipe end in turn, and finally tighten the outer groove flange and the step screw with nuts until the outer sealing ring is compressed and deformed to form a seal with the outer surface of the first pipe. The installation is complete.

[0012] S2. Test: Connect the pressure source to the threaded hole reserved in the outer groove flange through a quick connector, fill it with pressure medium, and maintain the pressure for the specified time to complete the test.

[0013] The advantages of the present invention are: the structure of the present invention can keep the bellows expansion joint in its original length after assembly, without being compressed or stretched, and the axial direction is limited, so that no axial tensile deformation will occur during the pressure resistance test, thereby reducing the subsequent shaping work. At the same time, unlike the general self-sealing that relies on the deformation of the sealing ring under the action of pressure, the present structure ensures the formation of a seal with the rough rusted surface by forcing the sealing ring to produce a large deformation, the sealing force can be adjusted, and the sealing reliability is high. This sealing structure can be used in pressure resistance tests and air tightness tests of various types of expansion joint products welded between bellows and straight pipes, without having to use a sealing method of welding a blind plate at the straight end. The pressure test device can be reused, and the test is convenient and quick, which greatly improves production efficiency and saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention.

[0015] Description of the serial numbers in the figure:

[0016] 1 is a stepped screw, 2 is a nut, 3 is an outer groove flange, 4 is an outer sealing ring, 5 is an outer boss flange, 6 is a bellows expansion joint, 61 is a first connecting pipe, 62 is a bellows, 63 is a second connecting pipe, 7 is an inner groove flange, 8 is an inner sealing ring, 9 is an inner boss flange, and 10 is a fixing bolt. DETAILED DESCRIPTION

[0017] Depend on Figure 1 The figure shows a pressure resistance test device for a metal bellows expansion joint for a falling film tube of the present invention, wherein the bellows expansion joint 6 comprises a first connecting pipe 61 with a shrinking treatment, a liner ring, a bellows 62, and a second connecting pipe 63. The test device comprises an outer groove flange 3 and an outer boss flange 5 matching the outer diameter of the first connecting pipe 61, and an inner groove flange 7 and an inner boss flange 9 matching the inner diameter of the second connecting pipe 63. An outer sealing ring 4 is arranged at the matching position of the outer groove flange 3 and the outer boss flange 5 on the outer side of the first connecting pipe, and an inner sealing ring 8 is arranged at the matching position of the inner groove flange 7 and the inner boss flange 9 on the inner side of the second connecting pipe. The device also comprises a stepped screw 1, one end of which matches the outer groove flange 3 and the outer boss flange 5, and the other end matches the inner boss flange 9, and they are respectively locked on the steps of the stepped screw 1 by nuts 2. The inner groove flange 7 matches the inner boss flange 9 by fixing bolts 10. As shown Figure 1 As shown, in this device, the groove flange refers to a notch provided at the position of the flange plate close to the connecting pipe, while the boss flange refers to a protrusion provided at the corresponding position. The protrusion cooperates with the notch. By adjusting the distance between the two, pressure can be applied to the sealing ring sandwiched in the middle gap to force it to deform, thereby increasing the pressure on the connecting pipe, that is, achieving a reliable sealing effect, and can adapt to certain non-roundness and surface roughness.

[0018] Preferably: a test hole connected to the testing machine is provided on the outer groove flange 3 .

[0019] Preferably, the inner diameters of the outer groove flange 3 and the outer boss flange 5 are slightly larger than the outer diameter of the first connecting pipe; and the inner diameter of the outer sealing ring 4 should be slightly smaller than the outer diameter of the first connecting pipe.

[0020] Preferably, the outer diameters of the inner groove flange 7 and the inner boss flange 9 are slightly smaller than the inner diameter of the second connecting pipe; and the outer diameter of the inner sealing ring 8 is slightly larger than the inner diameter of the second connecting pipe.

[0021] The above is slightly smaller than in order to ensure that the clearance can slide freely without affecting the seal. The slightly larger is to make the sealing ring have better initial sealing performance and be easy to place and move in a small range. The difference is usually within the range of 0.2-0.5mm.

[0022] Preferably: the outer groove flange 3, the outer boss flange 5 and the inner boss flange 9 have several through holes corresponding to the center holes for matching the stepped screw 1; the step size in the middle of the stepped screw 1 is larger than the thread size at both ends, and the steps formed are matched with the outer boss flange 5 and the inner boss flange 9 respectively, and the length of the step part should match the length of the expansion joint of the metal bellows used for the falling film tube, so as to ensure that the expansion joint is the initial length after the overall assembly of the test device and maintains the original length without being compressed during the test. When it is stretched by force, the outer groove flange 3 and the inner boss flange 9 at both ends are positioned under the action of the stepped screw 1 to play a role in limiting the stretching.

[0023] The test method of the device described in the present invention is as follows: S1. Installation: Install the inner sealing ring 8 into the groove of the inner groove flange 7, connect the inner boss flange 9 with the inner groove flange 7 and the inner sealing ring 8 with the fixing bolts 10, and keep the inner sealing ring 8 in a loose state to ensure that the inner sealing ring 8 can easily enter the second pipe; insert the step screw 1 into the through hole of the inner boss flange 9, and tighten it with the nut 2 to prevent the step screw 1 from loosening; assemble the second pipe end of the bellows expansion joint to the inner groove flange 7, and ensure that the end face of the second pipe is in close contact with the inner boss flange 9, and continue to tighten the fixing bolts 10 until the inner sealing ring 8 is compressed and deformed to form a seal with the inner surface of the second pipe; install the outer boss flange 5, the outer sealing ring 4 and the outer groove flange 3 at the first pipe end in turn, and finally use the nut 2 to tighten the outer groove flange 3 and the step screw 1 until the outer sealing ring is compressed and deformed to form a seal with the outer surface of the first pipe. The installation is completed.

[0024] S2. Pressure resistance test: Connect and seal the pressure source with the threaded hole 31 reserved in the outer groove flange 3 through a quick connector, etc., and fill it with pressure medium, and maintain the pressure for a certain period of time. The expansion joint should not leak under the specified pressure, the structure should not be obviously deformed, and the bellows should not be unstable. The maximum change rate of the wave pitch before and after pressurization should not be greater than 15%.

[0025] The structure of the present invention can keep the bellows expansion joint in its original length after assembly, without being compressed or stretched, and with the axial direction limited, so that no axial tensile deformation will occur during the pressure resistance test, thereby reducing the subsequent shaping work. At the same time, unlike the general self-sealing that relies on the deformation of the sealing ring under the action of pressure, the present structure ensures the formation of a seal with the rough rusted surface by forcing the sealing ring to produce a large deformation. The sealing force can be adjusted and the sealing reliability is high. This sealing structure can be used in pressure resistance tests and air tightness tests of various types of expansion joint products welded between bellows and straight pipes, without the need to use a sealing method of welding a blind plate at the straight end. The pressure test device can be reused, and the test is convenient and quick, which greatly improves production efficiency and saves production costs.

Claims

1. Pressure resistance test device for metal bellows expansion joint for falling film pipe, the bellows expansion joint comprises a first pipe with shrinking treatment, a liner ring, a bellows, and a second pipe, characterized in that: The test device comprises an outer groove flange (3) and an outer boss flange (5) matched with the outer diameter of the first connecting pipe, and an inner groove flange (7) and an inner boss flange (9) matched with the inner diameter of the second connecting pipe; an outer sealing ring (4) is arranged at a matching position between the outer groove flange (3) and the outer boss flange (5) on the outer side of the first connecting pipe, and an inner sealing ring (8) is arranged at a matching position between the inner groove flange (7) and the inner boss flange (9) on the inner side of the second connecting pipe; and the test device also comprises a stepped screw (1), one end of the stepped screw is matched with the outer groove flange (3) and the outer boss flange (5), and the other end is matched with the inner boss flange (9), and they are respectively locked on the steps of the stepped screw (1) by nuts (2); the inner groove flange (7) is matched with the inner boss flange (9) by fixing bolts (10); The groove flange (3) is provided with a notch at a position of the flange plate close to the pipe, and the inner boss flange or the outer boss flange is provided with a protrusion at a corresponding position, the protrusion matches the notch, and by adjusting the distance between the protrusion and the notch, pressure can be applied to the sealing ring sandwiched in the middle gap to force it to deform, thereby increasing the pressure on the pipe, that is, achieving a reliable sealing effect, and being able to adapt to a certain degree of non-roundness and surface roughness; The inner diameters of the outer groove flange (3) and the outer boss flange (5) are slightly larger than the outer diameter of the first connecting pipe; the inner diameter of the outer sealing ring (4) is slightly smaller than the outer diameter of the first connecting pipe; The outer diameters of the bosses of the inner groove flange (7) and the inner boss flange (9) are slightly smaller than the inner diameter of the second connecting pipe; the outer diameter of the inner sealing ring (8) is slightly larger than the inner diameter of the second connecting pipe; the step size in the middle of the stepped screw (1) is larger than the thread size at both ends, and the steps formed are matched with the outer boss flange (5) and the inner boss flange (9) respectively, and the length of the stepped part matches the length of the metal bellows expansion joint for the falling film tube.

2. The test device according to claim 1, characterized in that: A test hole connected to the testing machine is provided on the outer groove flange (3).

3. The test device according to claim 1, characterized in that: The inner diameters of the outer groove flange (3) and the outer boss flange (5) are slightly larger than the outer diameter of the first connecting pipe; and the inner diameter of the outer sealing ring (4) should be slightly smaller than the outer diameter of the first connecting pipe.

4. The test device according to claim 1, characterized in that: The outer diameters of the inner groove flange (7) and the inner boss flange (9) are slightly smaller than the inner diameter of the second connecting pipe; and the outer diameter of the inner sealing ring (8) is slightly larger than the inner diameter of the second connecting pipe.

5. A pressure resistance test method for a metal bellows expansion joint for a falling film pipe, using a test device as described in any one of claims 1 to 4, characterized in that: The method comprises the following steps: S1. Installation: Install the inner sealing ring into the groove of the inner groove flange, connect the inner boss flange with the inner groove flange and the inner sealing ring with fixing bolts, and keep the inner sealing ring in a loose state to ensure that the inner sealing ring can easily enter the second pipe; insert the step screw into the through hole of the inner boss flange and tighten it with a nut to prevent the step screw from loosening; assemble the second pipe end of the bellows expansion joint to the inner groove flange, and ensure that the end face of the second pipe is in close contact with the inner boss flange, and continue to tighten the fixing bolts until the inner sealing ring is compressed and deformed to form a seal with the inner surface of the second pipe; install the outer boss flange, outer sealing ring and outer groove flange in turn at the first pipe end, and finally tighten the outer groove flange and the step screw with nuts until the outer sealing ring is compressed and deformed to form a seal with the outer surface of the first pipe, and the installation is complete; S2. Test: Connect the pressure source to the threaded hole reserved in the outer groove flange through a quick connector, fill it with pressure medium, and maintain the pressure for the specified time to complete the test.

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